House of Commons

Letter from Sir Robert Chote to James Cartlidge MP – Chagos Islands deal

Dear Mr Cartlidge,

Thank you for your letter expressing concerns around the presentation of the cost of the Chagos Islands deal outlined by the Prime Minister in a press statement on 22 May. Specifically, he stated that

“£101 million a year is the average cost; the net overall cost is therefore £3.4 billion overall, that’s over the 99 years”.

You raised two concerns; first, that the Social Time Preference Rate used to calculate the figure of £3.4 billion was not the most appropriate measure, and second, that the source for the £3.4 billion had not been made available.

It is beyond the remit of the Office for Statistics Regulation (OSR) to determine the most appropriate discount rate to use for such calculations. But given the Government’s reference to the Office for Budget Responsibility (OBR) in defence of its chosen figure, we have confirmed with the OBR that they believe that this is a reasonable one to use when discounting the value of a lease.

The OSR has considered the transparency with which the calculation was communicated within the press statement. The press release provides a range of information for readers, including Notes for Editors. Our one concern is that by describing the £3.4 billion figure as the net overall cost, it was not made clear to the public that the figure was calculated using a discounting method.

In relation to the source of the calculation, the explanatory memorandum explains how the £3.4 billion figure was calculated, including reference to the use of the Social Time Preference Rate for discounting. We welcome that this information was made public at the time of the press statement in line with the principles of intelligent transparency. In future, we would encourage a link to this explanatory memorandum to be provided within the press statement in order to better support the public in understanding and scrutinising the figure.

We have raised these two points with the Prime Minister’s office and the Foreign, Commonwealth & Development Office.

Thank you again for raising this issue.

Yours sincerely,

Sir Robert Chote
Chair

James Cartlidge MP to Sir Robert Chote – Chagos Islands deal

Dear Sir Robert,

Misuse of statistics by the Prime Minister regarding the Chagos Islands surrender deal

I am writing to ask you to investigate claims made by the Prime Minister about the cost of the deal to surrender sovereignty of the Chagos Islands to Mauritius.

Yesterday, when asked about the cost of the deal, the Prime Minister claimed it would be £3.4 billion, even after accounting for inflation. This figure is inaccurate.^[1]

Independent analysis suggests that, once a conservative rate of inflation is accounted for, the true cost of the deal is likely to be in excess £30 billion. That’s a difference of £27 billion – a substantial amount that could mislead the public about the real financial cost.^[2]

I understand the government has used the Social Time Preference Rate (STPR) to calculate the figure used by the Prime Minister. The figure is therefore a representation of ‘social time preference’, not a representation of the direct cost to the taxpayer. However, the Prime Minister stated that:^[3]

‘That is the net cost, and the reason it is put in those terms is because it is how the Government accounts for it, it is how the OBR counts the cost, and it is the way public sector projects are measured. In other words, what’s the net cost is today? And that is £3.4 billion. Obviously over time, with inflation, then that is the net cost’^[4]

The Prime Minister has therefore misrepresented the figure by stating that it is a net cost when in reality it is a figure for the social time preference. Such discounting in the public sector is intended to allow the costs and benefits of different policies with varying time spans to be compared on a common basis. But in this case, it is being used as a statistical sleight of hand to hide the true cost to taxpayers of this surrender deal and appears to be a breach in the Code of Practice on Statistics which states that:

‘Statistics, data and explanatory material should be presented impartially and objectively’^[5]

Furthermore, the government has failed to publish the source statistics despite the Code of Practice on Statistics stating:

‘Policy, press or ministerial statements referring to regular or ad hoc official statistics should be issued separately from, and contain a prominent link to, the source statistics’^[6]

The government’s failure to publish the statistical methodology therefore appears to be in breach of the Code of Practice on Statistics.

As the UK Statistics Authority, your role is to promote transparency and accuracy in the use of public data. I therefore ask you to investigate whether the Prime Minister’s figure follows the Code of Practice on Statistics to make sure that public confidence in public statistics is upheld.

The public deserves clarity on this matter, especially given the government’s cuts to the Winter Fuel Payment and the tax hikes it has imposed on businesses. A transparent assessment will help to maintain trust in official figures.

I am placing this letter in the public domain.

Yours sincerely,

James Cartlidge MP
Shadow Secretary of State for Defence

Footnotes

^[1] In response to a question from David Shephard from the Financial Times yesterday, the Prime Minister said: ‘That is the net cost, and the reason it is put in those terms is because it is how the Government accounts for it, it is how the OBR counts the cost, and it is the way public sector projects are measured. In other words, what’s the net cost is today? And that is £3.4 billion’ (Prime Minister and Defence Secretary Statement on Chagos Islands, 22 May 2025, archived).
^[2] The Daily Telegraph, 22 May 2025, archived.
^[3] GOV.UK, UK/Mauritius, 22 May 2025, link.
^[4] Prime Minister and Defence Secretary Statement on Chagos Islands, 22 May 2025, archived.
^[5] ONS, Code of Practice for Statistics, 5 May 2022, link.
^[6] ONS, Code of Practice for Statistics, 5 May 2022, link.

Letter from Sir Robert Chote to Matt Vickers MP – police workforce figures

Dear Mr Vickers,

Thank you for your letter of 21 February regarding the use of police workforce statistics by Dame Diana Johnson, Minister of State for Police, Crime and Fire.

The claim in question was made during the debate on the Police Grant Report on 5 February 2025. The Minister stated,

“there were 149,769 police officers in March 2024, but in June – when the Conservative Government were still in power – that figure had been reduced by 1,232 to 148,536 officers.”

We examined this and determined that the figures cited by the Minister were published on 22 January 2025 as an annex in the Police workforce: 30 September 2024 bulletin. As such, the figures were publicly available at the time the claim was made.

However, we note that these figures are published management information rather than part of the regular statistics on police numbers, and so were not included or referred to in the separate data tables accompanying the bulletin.

We have discussed this approach with Home Office statisticians and will continue to support them in finding the best ways to publish management information outside of regular statistical releases, so that they are readily accessible when ministers and officials use them publicly. Thank you again for raising this matter with us.

Yours sincerely,

Sir Robert Chote
Chair

Matt Vickers MP to Sir Robert Chote – police workforce figures

Dear Mr Chote,

I am writing to formally complain about the use of unpublished statistics by the Minister of State for Police, Crime and Fire during a statement made in the House of Commons chamber when closing the debate on the Police Funding Settlement on 5^th February 2025.

During the statement, the Minister cited a police workforce figure “had been reduced by 1,232 to 148,536 officers” in June, despite the official publication schedule dictating that police workforce statistics are only released in March and September. As I understand it, the release of this figure is a clear breach of established statistical protocols and raises concerns about the proper and transparent use of official statistics.

The UK Statistics Authority’s Code of Practice for Statistics emphasises the importance of orderly release and preventing the misuse of statistics. The Minister’s announcement appears to contravene these principles by disclosing unpublished figures without making them publicly available in a consistent and transparent manner. As I understand it, no previous publications of police headcount numbers were announced in the month of June in previous years – making it impossible for trends or changes to be compared.

I request that the UK Statistics Authority investigates this matter and provides clarification on whether the Minister’s actions were in line with the Code of Practice. Additionally, I would appreciate a response outlining any steps the Authority may take to ensure ministers adhere to proper statistical procedures in the future.

Thank you for your attention to this matter. I look forward to your response.

Yours sincerely,

Matt Vickers
Member of Parliament for Stockton West
Shadow Minister of State for Police, Crime and Fire

Letter from Sir Robert Chote to Kieran Mullan MP – statistics on criminal records

Dear Dr Mullan,

Thank you for your letter regarding statements by Lord Timpson OBE, Minister of State for Prisons, Probation and Reducing Reoffending, on the proportion of the population with a criminal record.

The first statement was made by Lord Timpson in the House of Lords on 24 July 2024 and stated that:

“The criminal justice system exists to keep the public safe, but it should not hold back the one in four working-age people in the UK with a criminal record from getting jobs.”

This claim is based on information provided in an ad-hoc release by the Ministry of Justice in October estimating the number of individuals with a nominal record on the Police National Computer. As summarised within the release, there are a number of limitations for these data and the figure of ‘one in four’ should only be used as a high-level estimate.

Your additional concerns related to claims made in an article published by The Times on 9 January 2025. Within the article, the terms ‘criminal record’ and ‘criminal conviction’ are used seemingly interchangeably, which is imprecise – a criminal record is not the same as a criminal conviction – and the claims referring to criminal convictions are therefore not supported by the Ministry of Justice release. Furthermore, the article is also not always clear that the proportion of individuals with a criminal record relates specifically to the working age population (those aged 16-64) and not the whole population.

It is important that when using figures publicly, they are quoted accurately to best support public understanding on these issues. We have raised this matter with Lord Timpson’s office.

Yours sincerely,

Sir Robert Chote
Chair

Letter from Sir Robert Chote to Nick Timothy MP – costs associated with Illegal Migration Act

Dear Mr Timothy,

Thank you for your letter regarding statements made by the Home Secretary on 22 July about a change to the Illegal Migration Act (which would enable the Government to legally begin processing some asylum cases in the UK, rather than being obliged to remove those applicants from the UK first).

Specifically, you raised concerns that some of the estimated savings of £7 billion from this change was calculated by “double counting”: adding the costs of removing some applicants to the estimated costs of instead accommodating them in the UK.

On 22 July the Home Secretary told Parliament:

“Two and a half years after the previous Government launched it, I can report that [the Rwanda Migration and Economic Development Partnership] has already cost the British taxpayer £700 million… Making this one simple change will save the taxpayer an estimated £7 billion over the next 10 years.”

In response to your questions about this part of her statement, the Permanent Secretary of the Home Office wrote to you on 16 August. His letter said that “the Home Secretary’s statement included” the figure of £700 million of costs related to UK-Rwanda Partnership. He then wrote that “further detail is contained” within the Impact Assessment of the change to the law, from which the £7 billion of future savings was calculated. This indicated that the figures of £700 million and £7 billion were related.

Having discussed this issue with the Home Office, we established that the £700 million of costs are not included in the estimated £7 billion of savings outlined in the Impact Assessment and that they cover different time periods. The Permanent Secretary’s letter was not clear about the difference between these two figures, but since then the department has released a further breakdown of the £700 million which makes this more obvious.

It is important that Government correspondence is clear and transparent on issues of great public interest, referring precisely to published data. This enables Parliament and the public to understand and independently scrutinise government decision-making.

Yours sincerely,

Sir Robert Chote
Chair

Kieran Mullan MP to Sir Robert Chote – statistics on criminal records

Dear Sir Robert,

I am writing to express my concern regarding the use of a highly questionable statistic with significant limitations in the important field of criminal justice by a Government Minister

On the 24th July 2024, the Minister of State for the Ministry of Justice, Lord Timpson, stated in the House of Lords:

“The criminal justice system exists to keep the public safe, but it should not hold back the one in four working-age people in the UK with a criminal record from getting jobs.”

Lord Timpson was more recently quoted as repeating a variation of this claim in an interview with The Times published on 9 January 2025, stating:

“…around 25 per cent of adults in this country have a criminal conviction for a driving offence…”

This statistic appears to be based on data from the Police National Computer (PNC), compared against population data drawn from the statistical notice Estimate of the number of individuals of working age (16-64 and 16+) with a nominal record on the Police National Computer.

However, nominal records on the PNC include not only individuals with convictions but also those with cautions, pending prosecutions, and cases where no further action was required. Additionally, the PNC retains nominal records until at least 100 years after the individual’s birth, regardless of their date of death.

I am seeking clarity as to whether the dataset also contains records for individuals that are not resident in the UK. Furthermore, I understand individuals may appear in multiple categories, further complicating interpretation.

In response to a Written Parliamentary Question I submitted (available here: https://questionsstatements.parliament.uk/written-questions/detail/2024-11-11/13530/), the Ministry of Justice provided the following breakdown for offenders of working age:

Table 1. Proportion of the records on the Police National Computer (PNC) in each category specified, by offenders of working age

Outcome	Proportion
Conviction	74.6%
Caution	9.6%
Pending	4.6%
No further action	0.5%

This breakdown highlights that at least 15% of the records are non-conviction records, and the percentage could be even higher in the working age sub group.

Given the potential for this statistic to influence public perceptions and policymaking, I urge the Statistics Authority to review and provide advice on the use of this statistic, given its significant limitations. I recognise the need to encourage employers and others to give second chances to those with criminal records. However, we should not use statistics to normalise criminality in pursuit of that goal.

Thank you for your attention to this matter. I look forward to your response and would be happy to provide further information or discuss this issue in more detail.

Yours sincerely,

Dr Kieran Mullan MP
Member of Parliament for Bexhill and Battle

References

https://hansard.parliament.uk/Lords/2024-07-24/debates/6C3F5032-5C20-4B49-A20F-2D27E96E3809/King’SSpeech#contribution-61537CF3-D82A-41B7-8B07-2C5BA802C141

https://www.thetimes.com/uk/politics/article/ex-convicts-just-as-reliable-as-other-staff-says-prisonsminister-zsm5z2lqf

https://assets.publishing.service.gov.uk/media/671a27f0da8fb5e23e65a435/Estimate_of_the_number_of_working_age_people_with_a_nominal_record_on_the_Police_National_Computer_pdf.pdf

Letter from Sir Robert Chote to Andrew Griffith MP – claims on taxation

Dear Mr Griffith,

Thank you for your letter of 31 October about the changes to taxation announced in the Autumn Budget.

As set out in my letter of 4 June to party leaders, and referenced in your own letter, it is essential that, when making claims of this nature, underlying calculations, data sources and context are provided alongside the figures so that the average person can more fully understand any single figure cited in public debate.

These actions will ensure that when statistics and quantitative claims are used publicly, they are adhering to the principles of intelligent transparency and therefore enhancing understanding of the topics being debated.

Since the election, we have continued to affirm the importance of these principles for all and expect all those in government and in parliament to adhere to these in all forms of public communication.

Yours sincerely,

Sir Robert Chote
Chair

Nick Timothy MP to Sir Robert Chote – costs associated with Illegal Migration Act

Dear Sir Robert,

I am writing in regard to the claim made by the Home Secretary on 22 July that scrapping the retrospective element of the Duty to Remove in the Illegal Migration Act will save £7 billion of taxpayers’ money over the next ten years.

The Impact Assessment published by the Home Office appears to assume that no one in the cohort would have been removed to Rwanda or another country and would instead have remained in publicly funded accommodation for ten years. Notwithstanding the various assumptions and causes for concern about the Impact Assessment, the Home Office Permanent Secretary said to me in a letter dated 16 August 2024 that the Home Secretary’s statistic included the cost of sending the very same migrants to Rwanda. My concern is that the claim of £7 billion of savings was acquired through double counting.

As Chair of the UK Statistics Authority, I am requesting that you investigate this matter urgently. I would encourage you to ask the Home Secretary and the Permanent Secretary at the Home Office to publish all internal correspondence and the methodology related to the £7 billion figure so Parliament can fully understand whether it is an honest calculation.

Yours sincerely

Nick Timothy
Member of Parliament for West Suffolk

Andrew Griffith MP to Sir Robert Chote – claims on taxation

Dear Robert,

I’m writing to you following the Budget to correct the record on some statistics that were used before and throughout the election campaign.

On the 17th May the Conservative Party presented a dossier entitled ‘Labour’s Tax Rises’ to the public. This was predominantly based on a collection of HM Treasury costings which were undertaken using the formal Opposition Costing process that governments of all stripes have utilised.

Our dossier made the assertion that Labour’s policy commitments led to a black hole of over £10 billion a year by 2028-29 or nearly £38.5 billion over the next four years. This meant that the total burden on an average working household across the 4 years of a typical parliament would be £2,094.

While we were confident in the use of this figure, I note that you wrote to the then-Chairman of the Conservative Party stating that ‘when distilling these claims into a single number, there should be enough context to allow the average person to understand what it means and how significant it is’. At the time, the now-Prime Minister referred to such claims as ‘lying’ and accused us of doing so ‘deliberately’.

I regret to inform you that it now appears the £2,094 per household number is misleading.

In fact, the correct position appears to be significantly higher than this. After the Chancellor of the Exchequer’s Budget on 30 October 2024, it’s clear that the average per-household cost of Labour’s tax plans is in fact £2,237 – and this figure is for each year, rather than across a parliament.

I regret that this mistake occurred and that we – like so many people across the UK – took at face value the Labour Party claims at the election.

Yours sincerely,

Andrew

Letter from Sir Robert Chote to James Cartlidge MP – Chagos Islands deal

Related links

James Cartlidge MP to Sir Robert Chote – Chagos Islands deal

Misuse of statistics by the Prime Minister regarding the Chagos Islands surrender deal

Footnotes

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Letter from Sir Robert Chote to Matt Vickers MP – police workforce figures

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Matt Vickers MP to Sir Robert Chote – police workforce figures

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Letter from Sir Robert Chote to Kieran Mullan MP – statistics on criminal records

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Letter from Sir Robert Chote to Nick Timothy MP – costs associated with Illegal Migration Act

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Kieran Mullan MP to Sir Robert Chote – statistics on criminal records

Table 1. Proportion of the records on the Police National Computer (PNC) in each category specified, by offenders of working age

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Letter from Sir Robert Chote to Andrew Griffith MP – claims on taxation

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Nick Timothy MP to Sir Robert Chote – costs associated with Illegal Migration Act

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Andrew Griffith MP to Sir Robert Chote – claims on taxation

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