The UK Treasury has publicly denied Prime Minister Rishi Sunak's assertion that its unbiased staff calculated that the opposition Labour Party would "put up everyone's taxes by £2,000."

Sunak claimed during a televised discussion on Tuesday ahead of the July election, in which he and Labour leader Keir Starmer fought on subjects ranging from the cost of living and immigration to the status of the NHS.

"Independent Treasury officials have costed Labour's policies and they amount to a £2,000 tax rise for every working family," Sunak stated. The Conservative Party's leader later reiterated the accusation.

On the eve of the debate, James Bowler, the Treasury's most senior civil servant, reported that employees in his department had not drafted the figure, which appeared in a Conservative Party campaign brochure.

In a letter dated June 3 posted on X by senior Labour Party official Darren Jones, Bowler stated 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."

According to the campaign leaflet, Labour would need to find £38.5 billion ($49.2 billion) to satisfy all of its expenditure plans, either by borrowing or hiking taxes by "£2,094 per working household over the next four years," while claiming that "almost every costing" was conducted by the Treasury.

In his letter to Labour, Bowler stated that he had warned senior Conservative Party officials and advisors against claiming that the £38.5 billion number was based on an estimation from the Treasury, citing that any costings derived from other sources or organizations "should not be presented as having been produced by the Civil Service."

The Office for Statistics Regulation has now stated that it is looking into Sunak's statements, with a formal announcement coming as early as Thursday.

In a letter sent on Tuesday, chair of the statistics watchdog Robert Chote asked party leaders to ensure that numbers are utilized in an "appropriate and transparent" manner during the election campaign, rather than in a fashion "that has the potential to mislead."

Labour accuses Sunak of lying

Meanwhile, opinion surveys are divided on who won Tuesday's discussion. A YouGov snap survey of 1,657 viewers found that 51% believed Sunak performed better than Starmer.

However, in a survey of 1,153 viewers conducted by market research firm Savanta, 44% opted for Starmer, 39% for Sunak, and 17% remained unsure.

Bowler's letter might contradict Sunak's vow to rule with honesty, which he stated when he became prime minister in October 2022, as he faces a high-stakes election.

Opinion polls indicate that the Conservatives are on their way out of government, with Labour on track to win a UK election for the first time since 2005.

In a statement issued Wednesday, Labour said Sunak had "lied eleven times to the British people" about the party's tax proposals.  “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 stated in an email campaign message.

During the discussion on Tuesday, Starmer slammed the £2,000 ($2,560) number as "nonsense" and said it was based on "pretend" Labour policy.

A Conservative Party representative told CNN that it was time for Labour to "explain which of the policies which were Labour policy no longer are Labour policy."