Eurosceptic Tory MPs launch the Vote Leave campaign in February © AFP

Nearly two-thirds of the Conservative MPs who campaigned against David Cameron in the EU referendum have written to express support for the prime minister to remain in his job, in a move that looks set to kill off any early challenge to his leadership.

The gesture of support should see Mr Cameron through the first difficult hours after the result emerges in what has been a deeply divisive contest over Britain’s relationship with Europe.

The letter — signed by 86 MPs who supported the Vote Leave campaign — was sent to Downing Street on Thursday evening shortly after the polls closed.

Signatories included all five Cabinet ministers who had campaigned for Leave, including Michael Gove, justice secretary, and Chris Grayling, leader of the House. Boris Johnson, the former London mayor, also signed it.

More than 40 Eurosceptic Tory MPs have not signed the letter, which was organised by the backbencher Robert Syms and had been circulating among Conservative MPs for a couple of weeks.

The letter expresses full support for Mr Cameron to remain as prime minister whatever the outcome of the referendum. “Thank you for giving the British people a choice of their destiny,” it reads. “Whatever the British people decide, you have both a mandate and a duty to continue leading the nation [and] implementing our 2015 manifesto.”

To trigger a vote of confidence in Mr Cameron’s leadership, 50 MPs must write to the chairman of the backbench 1922 Committee. The Eurosceptics’ expression of unity effectively rules out the likelihood of Mr Cameron’s opponents within the party winning such a vote.

However, the prime minister faces a tough task in uniting his party sufficiently to govern. With a working majority in parliament of just 17, the Conservatives will struggle to pass legislation if the government is opposed by a relatively small group of hardcore backbench dissidents.

Iain Duncan Smith, the former party leader who quit the Cabinet this year in a row over cuts to disability benefits, did not sign the letter in support of Mr Cameron; nor did leading Leave campaigners Bernard Jenkin and Steve Baker.

The shoring-up of Mr Cameron’s position still casts doubt over the future of the chancellor, George Osborne. He played a leading role in stoking what Leave campaigners called the “Project Fear” tactics of the Remain camp. His warnings about the economic impact of Britain leaving the EU culminated in the threat of a post-referendum emergency Budget, which 65 Tory MPs publicly vowed to vote against.

Mr Baker told the BBC he had originally signed the letter of support for Mr Cameron but took his name off it this week in protest against what he called an escalation in the Remain campaign’s economic scaremongering. Mr Baker said the chancellor’s threat of a “punishment Budget” was “ludicrous” and many MPs were “extremely unhappy with it”.

© PA

He did support Mr Cameron continuing in office whatever the outcome of the referendum but he declined to express support for Mr Osborne, saying his future career was “a matter for the prime minister”.

Conservative MPs’ latest bid for unity echoes a letter written at the start of this year by the party’s new intake of MPs, who were elected for the first time in last year’s general election. They called on their more experienced colleagues not to let bitterness over Europe undermine the party’s ability to govern.

Several prominent members of the 2015 intake were among the signatories of Mr Syms’ letter. Andrea Jenkyns — a new MP and one of the letter’s signatories — called for unity in the aftermath of the referendum.

“We spent 18 years getting back in to majority government,” she said. “Now is the time to press on and govern for the good of everyone across Britain.”

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