David Cameron's chances of winning the next election are "remote", top Tory donor and election strategist Lord Ashcroft has warned.

Writing on the ConservativeHome website this morning, the former deputy chairman of the Conservative Party cited bookmakers' views that an overall majority for Labour is the most likely result in May 2015.

"With the polls as they are, and political prospects as they currently seem, it would be hard to argue that the bookmakers are seriously misguided. Any realistic survey of the political landscape surely shows the odds are against the Tories metaphorically as well as literally," he said.

Ashcroft added: "The odds on a Conservative majority look comparatively remote."

The peer concludes that the combination of traditional Labour voters and disaffected Lib Dems means Ed Miliband "ought to be able to put together 40 per cent of the vote without getting out of bed" at the next election.

However he said rather than listening to his "recalcitrant backbenchers" who want to see the party shift to the right in order to win back votes, the prime minister should press ahead with the "incomplete" modernisation of the Conservative Party.

Ashcroft said of the Conservative Party: "Too many people whose support it needs mistrust its motives, do not think it shares their priorities, and do not think it embodies the values it says it does."

"This applies particularly to those who thought about voting Tory in 2010 but decided against it. While they trust Cameron and Osborne more than Miliband and Balls to manage the economy, they do not think the Conservatives stand for fairness or opportunity."

Many Tory backbenchers, alarmed by the apparent rise in support for Ukip, have urged Cameron to take a stronger eurosceptic line and drop his more liberal plans including gay marriage.

However Ashcroft said that while Ukip is a danger, it would be even more dangerous for the party to think it could win people back through a greater emphasis on Europe combined with signals it shared "the disgruntlement with modern Britain that motivates many of Ukip’s supporters".