London CNN  —  The UK Treasury has flatly contradicted Prime Minister Rishi Sunak’s claim that its impartial officials had calculated that the opposition Labour Party would “put up everyone’s taxes by £2,000.” Sunak made the claim during a televised debate Tuesday ahead of July’s election, as he and Labour leader Keir Starmer clashed on issues ranging from the cost-of-living and immigration, to the state of the National Health Service. “Independent Treasury civil servants have costed Labour’s policies and it’s £2,000,” Sunak said. The Conservative Party leader later repeated the claim. On the eve of the debate, James Bowler, the most senior civil servant in the Treasury, said officials in his department had not been involved in producing that number. In a letter dated June 3, a copy of which was posted to X by senior Labour Party official Darren Jones, Bowler wrote that “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.” The Conservative Party document claims that Labour would have to find £38.5 billion ($49.2 billion) to meet all of its spending commitments, either borrowing the money or raising taxes by “£2,094 per working household over the next four years.” The document states that “almost every costing contained here has been conducted by (the) Treasury.” In his letter to Labour, Bowler said he had cautioned senior Conservative Party officials and advisers against suggesting that the £38.5 billion figure was based on Treasury analysis. He said that “any costings derived from other sources or produced by other organisations should not be presented as having been produced by the Civil Service,” adding that he had “reminded Ministers and advisers that this should be the case.” Photo issued by the Labour Party of a letter sent by Permanent Secretary to the Treasury James Bowler to senior Labour Party official Darren Jones. The Labour Party/PA Sunak narrowly won the debate Tuesday, according to an opinion poll. A YouGov snap poll of 1,657 viewers showed 51% thought he performed better, compared to 49% for Starmer. But Bowler’s letter could undermine Sunak’s claim to lead with integrity — a pledge made when he became prime minister in October 2022 — as he battles a high-stakes election. Opinion polls suggest the Conservatives are set to be booted from office, with Labour on course to win a UK election for the first time since 2005. LONDON, ENGLAND - MAY 29: People pass through the Bank area of the City of London on May 29, 2024 in London, England. In recent months, the UK's Chancellor of the Exchequer Jeremy Hunt has reportedly met with the boss of Shein, the Chinese-founded fashion retailer, to encourage the company to launch its initial public offering on the London Stock Exchange. London's reputation as a global financial hub has suffered in the wake of Brexit, compounded by an industry-wide slowdown in public offerings due to high interest rates and economic uncertainty. Carl Court/Getty Images Related article What happened to the UK economy? 5 charts break down the key election issue In a statement Wednesday, Labour said Sunak had “lied eleven times to the British people” about the party’s tax plans. “Labour will not raise taxes on working people. It’s the Tories who have made £71 billion of unfunded promises that will mean higher taxes and higher borrowing,” the party wrote in an emailed campaign message. During the debate Tuesday, Starmer dismissed the £2,000 ($2,560) figure as “nonsense” and said it was based on “pretend” Labour policies. A Conservative Party spokesperson said that its document on Labour’s tax plans “used clear Labour policies, their own costings or official (Treasury) costings using the lowest assumptions.” In a statement shared with CNN, the spokesperson added: “It is now for Labour to explain which of the policies which were Labour policy no longer are Labour policy.”