Outsiders in the race to replace Theresa May as Conservative leader are objecting to proposals to cull the crowded field of contenders.

The executive of the party’s backbench 1922 Committee meet on Tuesday to consider plans to increase the nomination threshold for taking part in the contest.

Senior figures, including James Brokenshire, the communities secretary, and ex-leader Iain Duncan Smith, have already called for the field of 13 contenders to be slimmed down.

They fear a drawn-out contest will delay the arrival of a new leader and eat into the time available to solve Brexit by the deadline of 31 October.

Kenneth Clarke, a former chancellor, warned that the contest was “in danger of becoming a rather tragic farce unless some order is brought into it”.

A mooted threshold of 12 MPs’ nominations – rather than the proposer and seconder previously required – could knock out outsiders like Rory Stewart, who has toured the country with a platform ruling out a no-deal Brexit, and Sam Gyimah, the only candidate arguing for a second referendum.

Tory leadership rules state only that the 125,000-strong membership in the country will elect the new leader from a shortlist of two drawn up by MPs, leaving it up to the 1922 Committee to draw up the rules for narrowing down the field.

Previous contests have seen twice-weekly ballots of MPs, each removing the least popular candidate until only two remained. But with 13 in the race, this process could take more than a month to produce a pair of rivals for the final face-off, delaying the choice of a leader until late in the summer.

Sam Gyimah says he will be joining Conservative leadership race

Nigel Evans, a joint secretary of the committee, said that requiring each candidate to gather 10 nominations on top of their proposer and seconder would allow the contest to be kept to “manageable proportions”, reducing numbers in the first round to six or seven.

“If we don’t implement rules which allow us to whittle away those with little support, the whole process will be totally unwieldy,” he said.

None of the contenders has spoken out publicly against a change in rules.

But it is understood that some are privately angry. A source close to one of the campaigns said a rule change at this stage might give an unfair advantage frontrunners such as Boris Johnson and Dominic Raab, who have been outside the government in recent months.

“It would be remarkable for the rules to change in favour of those who quit cabinet or their ministerial posts to get a head start on their leadership campaigns,” said the source.

Of the declared candidates, only Mr Johnson, Mr Raab, Jeremy Hunt, Michael Gove, Sajid Javid and Matt Hancock have enough declared supporters to pass a 12-nomination threshold.

Mr Stewart, Mr Gyimah, Mark Harper, Kit Malthouse, Esther McVey, James Cleverly and Andrea Leadsom could find themselves knocked out before the contest has begun.

Mr Johnson kicked off his campaign proper on Monday with a launch video showing him on the doorstep in the campaign for the Peterborough by-election and promising to “deliver Brexit and unite our fantastic country”.

The former foreign secretary is seen repeating his commitment to take the UK out of the EU on 31 October, “deal or no deal”. And he boasts of achieving a 20 per cent crime reduction in London as mayor, in part through the use of stop-and-search tactics.

Mr Johnson also launched a pledge to close the “funding gap” between schools in different areas of the country, with per-pupil support in some parts of London at £6,800 compared to £4,200 elsewhere in the UK.

Who could succeed Theresa May as Conservative leader? Show all 9 1 /9 Who could succeed Theresa May as Conservative leader? Who could succeed Theresa May as Conservative leader? Boris Johnson Former foreign secretary Boris Johnson has long been hopeful, he previously stood in the leadership contest that followed the Brexit vote and has at many times since been thought to be maneuvering himself towards the goal. He remains a darling of the party's right wing, particularly those in the ERG, and is the most popular choice among Tory voters but his leadership bid would be fiercely opposed by many MPs PA Who could succeed Theresa May as Conservative leader? Michael Gove Environment secretary Michael Gove is another member who has long wanted to be leader. He has lately been known for rousing his party in the commons, his recent speeches on the Brexit deal and Labour's no confidence motion have overshadowed the Prime Minister's. He has been loyal to the Prime Minister, partly to shed his reputation as a backstabber who abandoned Boris Johnson to stand against him in the 2016 leadership election Getty Who could succeed Theresa May as Conservative leader? Dominic Raab Former Brexit secretary Dominic Raab has emerged as a favourite to be the Brexiteer candidate in a contest to succeed to Ms May. He displayed a grip on detail in his role as Brexit secretary. When asked recently if he would like to become prime minister he replied "never say never" Getty Who could succeed Theresa May as Conservative leader? Rory Stewart International development secretary Rory Stewart is pitching himself as the sensible candidate, promising to rule out both a second referendum and a no-deal Brexit. He was only recently promoted to the cabinet, previously serving as prisons minister, where he caught headlines with a pledge to resign if he could not reduce levels of violence within a year PA Who could succeed Theresa May as Conservative leader? Esther McVey The former work and pensions secretary announced that she will be standing for the leadership when May leaves. McVey is the first to explicitly state that she intends to stand. She resigned from the cabinet in protest over May's Brexit deal AFP/Getty Who could succeed Theresa May as Conservative leader? Sajid Javid Home secretary Sajid Javid is said to have a plan in place for a leadership race. He made headlines over Christmas when he declared that people smuggling over the English channel was a "major incident" and more recently when he revoked the citizenship of ISIS bride Shamima Begum. Son of a bus driver, he wants the Conservatives to be seen as the party of social mobility PA Who could succeed Theresa May as Conservative leader? Jeremy Hunt Foreign secretary Jeremy Hunt was recently thought to be the favourite in the event of a leadership race as he could sell himself as the man to unite the party. Critics worry that his long stint as health secretary could return to haunt him at a general election. He has reportedly been holding meetings with Tory MPs over breakfast to promote his leadership PA Who could succeed Theresa May as Conservative leader? Andrea Leadsom Following the Prime Minister's second defeat over her Brexit deal, Leader of the house Andrea Leadsom hosted a dinner party at which "leadership was the only topic of conversation", The Times heard. Leadsom ran against Theresa May in the 2016 leadership election before dropping out, allowing May to become Prime Minister AFP/Getty Who could succeed Theresa May as Conservative leader? Priti Patel Former international development secretary Priti Patel is thought to be positioning herself as a contender. One MP told The Independent "she knows she's from the right of the party, the part which is going to choose the next leader, so she's reminding everyone she's there." Patel left the government late in 2017 after it emerged that she had held undisclosed meetings with Israeli officials PA

But Ed Davey, the Liberal Democrats’ home affairs spokesperson, challenged his claims on crime, arguing that figures show the actual fall in crime in the capital was 15 per cent during Mr Johnson’s time in office and that a Home Office analysis found “no statistically significant crime-reducing effect” from extra searches for weapons.

“For Johnson to kick off his leadership campaign with a lie is at least very on-brand,” said Davey.

Unofficial tallies of declarations of support put Mr Johnson near the head of the pack, with more than 30 MPs, followed by Mr Gove and Mr Hunt slightly below 30 and Mr Raab and Mr Javid around 20.

Mr Brokenshire used a speech in London to urge those with little chance of winning the race to consider dropping out, warning: “We simply do not have the luxury of weeks of navel-gazing or days and days of whittling candidates down to the final two and talking to ourselves.

“I say gently to some of my colleagues who have put themselves forward for what has been described as the Grand National of political contests: please think carefully.

“If you already know it’s going to be a bit of a struggle to get over the first fence, let alone Becher’s Brook ahead, then maybe you should pull up.”