Theresa May's stay of execution is being seized on by enemies of Boris Johnson - but his supporters claim Tory MPs have 'bottled it', it was revealed today.

The Prime Minister has been given some breathing space after senior Tories rejected plans that could have seen her forced from office within weeks.

In a significant setback for Mrs May's Brexiteer critics, the ruling executive of the 1922 Committee of MPs blocked a bid to change the leadership rules to allow a fresh vote of confidence in her.

Rumours are now growing that Mrs May could bring back her deal next week - if passed she would then quit.

One 1922 committee member told The Sun: 'Getting rid of Theresa before Brexit is done means getting Boris, Boris would mean No Deal, and No Deal would mean a general election. And that would be the end of Brexit altogether'.

Theresa May, pictured in Belfast yesterday, is safe from a Conservative leadership challenge until December after backbenchers rejected a change to party rules - with some saying it is good news because it will 'stop Boris'

The chair of the 1922 Committee, Sir Graham Brady, said last night it would be 'a surprising response' if Mrs May suggested she might stay on as late as December this year - but the backbenchers rejected a rule change to force her out early.

Sources on the 1922 committee said the plan, which was championed by Eurosceptics furious at her failure to deliver Brexit, was narrowly defeated by nine votes to seven.

Instead, the committee agreed to ask the Prime Minister to set out a 'timetable' for her departure. No10 last night gave no indication of when Mrs May would respond – or if she would agree to name a date for departure.

One senior Brexiteer said the committee had 'bottled it'.

Theresa May's popularity among Tory members hit rock bottom today as she was warned she could face a fresh leadership challenge within weeks unless she sets out a timetable for her departure.

The Prime Minister's approval rating has dropped by more than 20 points in a month to minus-73.5. She is now the least popular member of the cabinet, after overtaking previous incumbent Transport Secretary Chris Grayling, who is on 71.1 points.

Brexiteer Andrea Leadsom is the most popular - on plus-40.6 - followed by Liz Truss, Jeremy Hunt and Scottish Tory leader Ruth Davidson, who also has a seat at Mrs May's ministerial table, a poll of Tory supporters by ConservativeHome has revealed.

But Boris Johnson is streets ahead in the race to replace Theresa May as Tory leader and has an 18 point lead over his nearest rival Dominic Raab - and would also win in head to heads

Another survey on the influential Conservative Home website shows 33 per cent of people want Mr Johnson to take over as party chief.

Sir Graham Brady (pictured left), chairman of the 1922 Committee, said the backbench group had rejected a rule change but demanded a 'roadmap forward' on the PM's future

He enjoys twice the support of his nearest rival Dominic Raab on 15 per cent, followed by Michael Gove on eight per cent, Jeremy Hunt on six per cent and Sajid Javid on five per cent.

The poll, published today, shows Jacob Rees-Mogg, David Davis, Matt Hancock, Esther McVey and Penny Mordaunt on just two per cent.

ConHome chief Paul Goodman said: 'Boris' resignation catapulted him to the front of the queue as the main Conservative opponent of Theresa May’s EU policy. And the worse she does, the more he thrives.

'The postponement of Brexit, the talks with Jeremy Corbyn, the return of Nigel Farage, the looming European elections, the sense of drift and paralysis…all these have bumped him up to his highest total since last August'.

But the news has kick-started a 'Stop Boris' plot among remainer Tory MPs to orchestrate voting to stop him getting into the final two leadership candidates party members across the country will vote on.

Tory rules dictate that MPs whittle down the candidates and moderates hope they can squeeze out hard Brexiteers in favour of more moderate candidates who would pursue a softer Brexit, including second favourite Michael Gove.

One plotter said: 'Once we know the numbers of candidates and the names but it will come down to blocks of votes'.

Mrs May has promised to step aside when her Brexit deal is approved by Parliament.

But with doubts over how long that could take – and Brexit now delayed until the end of October – her critics are demanding that she names a date for her departure regardless of whether her deal is approved.

Sir Graham Brady said Tory MPs wanted a 'clear road-map forward' about Mrs May's future 'in all circumstances'. She faced a vote of no confidence in December after the number of Tory MPs demanding one reached 48 – the number required to trigger a contest.

A Conservative Home poll has found that Theresa May is now the least popular cabinet member after her rating dropped by 20 points in a month

Mrs May won the vote by 200 to 117, and the party's existing rules state that if a leader wins, 'no vote of confidence shall be called for a period of at least 12 months', meaning she cannot be challenged until this December.

But Eurosceptic MPs angry over her failure to leave the EU and the decision to open talks with Jeremy Corbyn have led to pressure to change the rules.

Under one proposal discussed last night, the 'grace period' would have been cut to six months, allowing a fresh challenge on June 12.

The drive for change was led by senior Brexiteers, with the 1922 Committee's executive secretary Nigel Evans saying that the process for selecting a new leader 'can't start soon enough'.

Pauline Latham, another committee member, yesterday backed the call, saying: 'I would like Theresa May to go. I would like us to have a new leader who could have another look at this whole process and actually negotiate with Brussels.'

But other senior Tories railed at the idea of ripping up the rulebook to give Brexiteer MPs another chance to topple her. Former minister Robert Halfon said: 'We are the Conservative Party – not some kind of Stalinist party who change the rules in order to have a show trial.

'Things are difficult at the moment, but we have to get on with the job. We have got council elections next week, we have got Brexit to deliver – we need to stop squabbling with each other and concentrate on that.'

Health Secretary Matt Hancock said: 'Changing the prime minister will not change what we need to do to deliver Brexit.'

The decision to reject the rule change was greeted with relief in Downing Street last night. But sources said the PM would have to consider the request for a resignation timetable.

Allies insisted she was not trying to cling to office, but believed she had a duty to deliver Brexit.

One said: 'There is a great irony in the fact she is facing these calls when she is saying she accepts there must be new leadership for the next phase and is actively trying to bring that about by delivering Brexit.'

Last night's decision may only prove to be a stay of execution if the forthcoming local and European elections turn out badly for the Tories. Former leader Iain Duncan Smith said: 'I think it's inconceivable that the Prime Minister would go on beyond the beginning of the summer break, it's just not feasible, because there is a window for a future leader to be elected and that is in the summer.'

Downing Street yesterday said Mrs May was still considering bringing back her deal – perhaps as soon as next week – in the hope of avoiding European elections on May 23. Labour sources indicated they would continue to oppose the legislation.