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David Cameron received another blow last night as the deputy treasurer of the Conservative Party resigned, partly in protest at his leader’s alleged shift to the right.

With Labour seeking to calm speculation that Gordon Brown might call a snap autumn election, the sudden decision of Johan Eliasch to quit the post he held for four and a half years handed the Labour Party fresh ammunition for its claim that Mr Cameron had reverted to policies promoted by his predecessors.

Although two polls released last night suggest that Mr Brown’s lead is narrowing, allies of the Prime Minister dismissed claims that he is preparing to hold a snap election. Claims that the speculation was being promoted by the Tories to mask a “power struggle” within the ranks will gain credibility from Mr Eliasch’s resignation.

After a week in which Mr Cameron took fresh hardline positions on crime and immigration, sources close to Mr Eliasch toldThe Timesthat he was upset that Mr Cameron was taking his party to the right at a time when it should be focusing on capturing the centre ground. It should not be moving away from the consensual style of politics adopted by Mr Cameron when he took over, the sources said.

“Changing direction in mid-course is a mistake,” a source close to Mr Eliasch said. An added headache for the Tory leadership is that Mr Eliasch, 45, made a £2.6 million loan to the party, which is still outstanding. Sources close to the Swedish businessman, who is chairman of the sporting goods manufacturer Head, would not comment on suggestions that he might call in the loan. Such an action, although unlikely, may cause unexpected problems for the party.

The Conservatives will be hit with a further blow today if, as expected, Gordon Brown announces that another Tory MP is prepared to work for him. Although the unnamed MP will not defect, it is understood that he will be put in an role that will illustrate the Prime Minister’s desire to work with a number of “outsiders”.

The stated reason for Mr Eliasch’s resignation is that he wants to spend more time working on climate change and with his environmental pressure group, Cool Earth, which gives individuals and groups, including schools and businesses, the chance to fund rainforest protection on a large scale.

His friends made plain that he had not been happy with Mr Cameron’s attempts to shore up his position with the Right after the row over grammar schools and his trip to Rwanda during the floods. One said: “David Cameron was in the right place and doing the right thing. This move to the right is not the correct thing to do.”

Friends say that he believes it could cost Mr Cameron the next election. “The polls only a short time ago showed that Mr Cameron was doing the right thing in going for the centre ground. To move away from that because Gordon Brown has turned out to be a better opponent than expected is a mistake.”

The move underlines Mr Cameron’s dilemma in trying to keep both wings of his party on board. The modernising faction has been voicing private dismay at Mr Cameron’s recent utterances on immigration and Europe, but key parts of the party, including many of its financial backers, are pleased with the shift.

Friends said that Mr Eliasch was not upset by any one particular speech or policy announcement but by what he saw as the general picture. “He believes elections are won on the centre ground and he believes Mr Cameron is moving away from it,” the source said.

Mr Eliasch has been closely involved in recent Tory politics and served on the advisory board of the Centre for Social Justice, Iain Duncan Smith’s think-tank. Friends said that he was unlikely to switch sides to Labour. “Basically he is very involved with his climate change work and his sporting companies and that is what he will concentrate on from now on.”

Douglas Alexander, Labour’s general election co-ordinator, dismissed talk of a snap poll, saying that talk of Mr Brown calling an election as early as this week were nonsense.

A poll in The Independent puts Labour and the Tories neck and neck on 36 per cent. The monthly survey by ComRes, formerly CommunicateRe-search, shows Labour and the Tories on 36 per cent. The Liberal Democrats are on 15 per cent. Another YouGov poll for GMTV has Labour on 38 per cent, the Tories on 35 per cent and the Lib Dems on 15 per cent if there was an immediate general election.

There is widespread support for such an early poll: 42 per cent of voters told the pollsters they would like to see an election this year and 22 per cent were actively opposed.

Mr Alexander, who is also International Development Secretary, told BBC News 24: “The claim that the Conservatives made that we are announcing an election this week, it’s no surprise, is nonsense.”

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