One of the Conservative Party’s biggest donors is withdrawing his support over the “irresponsible” way in which Prime Minister David Cameron has handled the EU referendum campaign.

Edi Truell, a pensions advisor, said Mr Cameron’s warning this weekend over the alleged damage Brexit would do to pensions was the final straw in a long list of “unfair” claims by the Remain campaign.

He told the Daily Telegraph that “the machinery of Government is being abused” by the campaign to keep Britain in the European Union (EU) and said he would not be giving any more money to the Conservatives while David Cameron remained Prime Minister.

Mr Truell, who has donated over £270,000 to the party since 2010, said he would only give more money to the party if Boris Johnson or Michael Gove, senior ‘Leave’ campaigners, become leader.

“I think Boris, Michael Gove and team have done a sterling job, a brave job, and I would be only too pleased to support them and, in my view, the genuine Conservative party in the future,” he said.

“I’m not prepared to support the current regime given the way they have been going about things.”

He added that he was “staggered” by claims made by Mr Cameron about how bad Brexit would be, describing Treasury figures that predict economic meltdown as “fantasy”.

“The much greater risk is remaining within the EU, they’ve got explicit plans to destroy British pensions,” Mr Truell said.

“All the final salary funds will go bankrupt and their companies will go bankrupt supporting them, that’s about 8,000 pension funds in the private sector.”

Mr Truell’s intervention comes just days after Margaret Thatcher’s Defence Secretary Sir John Nott said he was suspending his membership of the Conservative Party over the conduct of the Remain campaign.

Sir John accused the Prime Minister of “alienating” supporters, adding: “I was shocked when Cameron and, in particular Osborne, launched into to this fairly frenetic campaign in favour of the EU.”

“They launched very early into this attack, this description of all the horrors that would happen if we exit. I just listed to this and thought, ‘this is complete nonsense’.”