The Conservatives have defended their claim that Labour would raise taxes by £2,000 after it emerged a senior Treasury official had warned them not to say civil servants were behind the claim.

The Prime Minister repeatedly highlighted the claim during his ITV head-to-head debate with Sir Keir Starmer, claiming “independent Treasury officials” have costed Labour’s policies “and they amount to a £2,000 tax rise for everyone”.

But the Treasury’s permanent secretary James Bowler said ministers had been told not to suggest civil servants produced the figure at the heart of the Tory attack.

The claim comes from a document produced by the Conservatives which made a series of assumptions to estimate the cost that might be attached to potential Labour policies.

Bournemouth Echo: The Treasury's senior official has reminded ministers not to claim that civil servants were behind the Conservative allegation that Labour's plans would cost more than £38 billionThe Treasury's senior official has reminded ministers not to claim that civil servants were behind the Conservative allegation that Labour's plans would cost more than £38 billion (Image: The Labour Party/PA Wire)

It claimed that the difference between the money that Labour would raise from its policies and the amount it would spend would be a deficit of £38.5 billion over four years, amounting to around £2,094 for every working household.

Some of the estimates in the document have been carried out by civil servants at the Treasury, using assumptions provided by politically appointed special advisers.

But Mr Bowler said the headline figure used by the Tories should not be attributed to impartial civil servants.

In a letter to Labour’s shadow Treasury chief secretary Darren Jones he said the £38.5 billion total for Labour policies in the Tory document “includes costs beyond those provided by the Civil Service”.

“Costings derived from other sources or produced by other organisations should not be presented as having been produced by the Civil Service,” he said in a letter to Mr Jones on June 3.

“I have reminded ministers and advisers that this should be the case.”

Energy Secretary Claire Coutinho repeated the claim on Wednesday, saying it was based on “official costings from the Treasury”.

She told BBC Breakfast: “I’ve worked in the Treasury and I can tell you that these are brilliant, independent civil servants and they would not be putting anything dodgy in there.”

But shadow paymaster general Jonathan Ashworth said: “I feel that Rishi Sunak was exposed as desperate last night – desperately lying about Labour’s tax plans, making accusations about Labour’s tax plans which are categorically untrue – Labour will not put up income tax, will not put up national insurance, will not put up VAT.”

He told BBC Radio 4’s Today programme: “Rishi Sunak was resorting to lying because he is desperate and what do desperate people do when in a corner? They lie.

“We saw it with Boris Johnson over parties in Downing Street in lockdown, and Rishi Sunak has exposed himself as no better and no different than Boris Johnson with his lies last night.”

Polls suggested neither Mr Sunak nor Sir Keir landed a knockout blow during the ITV clash on Tuesday night.

A snap poll from YouGov suggested the Prime Minister performed marginally better, with 51% making him the winner against 49% for Sir Keir among people who expressed a preference.

But a Savanta survey pointed to a more convincing victory for Sir Keir on 53%, ahead of Mr Sunak on 47%, excluding those who said they did not know.

Perhaps the most telling findings from the YouGov survey were that 62% found the ITV debate frustrating and just 17% found it a helpful exercise.