May the force be with you: Leadership rumours destabilise Cameron

Tory MPs were becoming increasingly confident in speaking up for potential leadership challengers today, as Theresa May was celebrated for her "fantastic credentials" for the top job amid continued rumours about her ambition.

Media secretary Maria Miller praised the home secretary after a barely-concealed leadership pitch at ConservativeHome's conference yesterday, in which she suggested the Tories should pledge to pull out the European Court of Human Rights (ECHR) at the next election.

"By 2015 we'll need a plan for dealing with the European Court of Human Rights. And yes, I want to be clear that all options – including leaving the convention altogether – should be on the table," she said.

Bookmakers William Hill have cut the odds on May becoming the next Tory leader from 12/1 to 4/1 .

"It appears to be an open secret amongst Tory insiders that Theresa May is planning a leadership bid at some stage – and plenty of punters believe she would have a decent chance of succeeding David Cameron, "said spokesman Graham Sharpe.

Up to 25 Conservative MPs are understood to be planning a leadership push against David Cameron if the party's fortunes continue to tumble, the Telegraph reported.

Tory rules allow for a leadership contest if 46 Mps are prepared to sign a letter demanding it. A hardcore of disgruntled Conservatives plan to attempt the manoeuvre if George Osborne's Budget is badly received or if the party suffers a severe drubbing in the local elections in May.

The threats come after the party slipped to third place in Eastleigh and the publication of a damning opinion poll from Tory donor Lord Ashcroft.

The survey of marginal constituencies found Labour was on course for a majority of 84 in 2015.

Meanwhile, an Observer poll put Ukip on 17%, well above the Lib Dems' eight per cent and only ten points below the Tories' 27%.

Most rebellious Tory MPs want a further shift to the right to address the threat from Ukip, with harder pledges on an EU referendum, probably in the form of draft legislation with the wording of the referendum and details of how the UK would leave the union.

The problem with the strategy is it had little effect in Eastleigh, where Ukip surged despite Cameron's EU pledge and a right-wing campaign focusing on welfare and immigration.

May continues to hold 'tea-room surgeries' with fellow Tory MPs, boosting her popularity in the party.

Meanwhile, there are still rumours around Phillip Hammond, who would be expected to stand with her as a potential chancellor, in what Westminster had dubbed the 'Top Gear' ticket because of the pair's names.

Even Liam Fox – regarded as a leading light on the Tory right since he had to step down as defence secretary – is still a focus for leadership rumours, not least because of the speech he will deliver in Westminster this week entitled 'the right approach for the economy'.

Ed Miliband highlighted the rumours around May last week when he told the Commons he was "looking forward to facing her in opposition".