Conservative Party chairman Richard Holden has used a letter from cabinet secretary Simon Case in an attempt to counter allegations that the work of HM Treasury officials has been misrepresented by the party.
It comes after accusations that the party overstated civil servants' role in its calculations that Labour government would increase taxes by £2,000 per household.
Holden published the two-page letter from Case on X this morning. However it does not appear to contain new information, and underscores that Treasury officials were not responsible for the entirety of the workings behind the figures.
"I have received a response from the cabinet scecretary," Holden wrote. "He has confirmed that 21 costings of Labour’s policies were produced by civil servants from HM Treasury and other relevant departments.
"Contrary to Labour's claims he also confirmed that the letter from the Treasury permanent secretary made no reference to the prime minister."
Case's letter, dated June 10, follows last week's live ITV wrangle between prime minister Rishi Sunak and Labour Party leader Sir Keir Starmer over figures originally included in the Conservative Party's Labour's Tax Rises document, which was published in May.
The 24-page paper costs 27 Labour policies at £38bn and is the basis for the claim that a Labour government would mean a £2,000 tax rise for all households.
Sunak said on live TV that the figures were produced by independent civil servants at HM Treasury. Starmer dismissed the figures in the debate, and subsequently accused Sunak breaching the ministerial code by "lying deliberately" about the numbers.
Some of the costings were based on figures produced by Treasury officials under the "opposition costings" system, where ministers and special advisers can ask officials to assess the impact of rival parties' policies.
After the debate, a letter from Treasury permanent secretary James Bowler emerged in which he distanced his department from the £38bn total provided in the Labour's Tax Rises document, from which the £2,000 – or, to be precise, £2,094 – figure for individual households derives.
"Civil servants were not involved in the production or presentation of the Conservative Party's document Labour's Tax Rises or in the calculation of the total figure used," Bowler said.
"Any costings derived from other sources or produced by other organisations should not be presented as having been produced by the civil service."
UK Statistics Authority chair Sir Robert Chote said Sunak's conduct in relation to the figures had been damaging for public trust.
In a BBC interview broadcast last night, Sunak acknowledged that not all of the figures had been produced by HM Treasury officials, but sidestepped the suggestion that the way the total figures had been presented was really the work of party researchers.
"There are 27 different policies that underpin that figure. Of those 27, 21 are produced by independent treasury officials – they are available online for people to see, three come from other government sources, two come from the Labour Party themselves and one comes from an independent investment bank," he said.
"You tot them all up, divide by the number of households and that's how you get £2,094 for every working family in our country."
In the letter published by Holden on X this morning, cabinet secretary Simon Case confirms that civil servants working for HM Treasury and other departments produced 21 of the costings contained in the Conservative Party document.
Case said the costings had been done in accordance with civil service guidance, and that they had been "produced on assumptions provided by special advisers on behalf of ministers".
Case's letter was written in response to an approach from Holden on 6 June, in which the Conservative Party chair also sought confirmation that Bowler's earlier letter had made no reference to prime minister Rishi Sunak.
Holden referenced comments from shadow chancellor Rachel Reeves, who said on 5 June that Bowler's letter confirmed that prime minister Rishi Sunak had lied in in the ITV debate.
"The letter obviously did no such thing," Holden wrote. "I would therefore be grateful if you would confirm back to me that the letter in question did not say or suggest that the prime minister lied."
Case's letter acknowledges that Bowler's 3 June communication said nothing about the prime minister. However the letter was written and sent before the 4 June ITV debate in which the £2,000 claims came to the fore. It specifically refers to claims in the Labour's Tax Rises document.
Opposition costings "needs to end"
On Friday, public-sector leaders' union the FDA wrote separately to Sunak and Starmer, urging them to end the "opposition costings" tradition.
General secretary Dave Penman said placing impartial civil servants in the position of producing figures designed to portray ministers' political rivals in a negative light merely served to drag officials into election-time "mudslinging".
"The civil service is not independent. It offers impartial advice but it loyally serves the government of the day, no matter the colour," Penman said.
"That makes this whole practice of using the civil service to cost opposition policies highly questionable; they will never be ‘independent’ calculations as they’re based on politically partial assumptions and completed at the direction of ministers.
"Dragging civil servants into political mudslinging during an election campaign undermines the impartiality of the civil service at a crucial time when they may be preparing to support a change of government.
"The permanent secretary to the Treasury should never be put in a position to comment publicly on opposition party policies and the circus we have seen play out over the last week is in nobody’s best interest."
Penman said it was time to end the use of civil servants to cost policies of opposition parties for all future elections.
"Whoever's in power is going to be tempted to try and create a veneer of independence around these kind of Treasury calculations to help their party politically," he said. "That is not what the civil service is for."