The Tory leadership contest is a crowded race, with Foreign Secretary Liz Truss one of the most recent to officially join the field of 11 candidates vying for the top job.

But the number could be quickly slashed.

Elections are taking place on Monday afternoon for the executive of the 1922 Committee, a powerful backbench panel chaired by Sir Graham Brady which has the ultimate responsibility for setting the rules in any Conservative Party leadership contest.

The newly-elected executive will meet immediately to decide the rules and procedures for this race to replace Boris Johnson, and Sir Graham will meet the Tory Party board to set the timetable, with an announcement expected at about 7pm.

To avoid the contest dragging on, the candidates could be whittled down to a final two before the start of MPs’ summer holidays next Thursday.

Bob Blackman, joint-executive secretary of the 1922 Committee, told Sky News: “We’ve got to slim down the list of candidates pretty quickly to two.

“And the one thing that we’re committed to do is to achieve getting to two candidates by Thursday July 21.

“That means that we’ll hold a succession of ballots over the next few days in order to get to that position.”

The 1922 Committee will discuss raising the threshold of support needed to enter the race, with Mr Blackman indicating this could be 20 MP nominations.

He said: “The view is that candidates to get on the ballot paper should demonstrate a broad swathe of support amongst Conservative MPs.

“So we’re looking at a proposer, a seconder and either 18 supporters or possibly more supporters in order to reduce that list.”

This could lead to complaints that lesser-known contenders are disadvantaged compared with household names such as ex-chancellor Rishi Sunak.

Mr Sunak currently has the most nominations, followed by trade minister Penny Mordaunt and Foreign Affairs Committee chairman Tom Tugendhat.

Newly-appointed Foreign Office minister Rehman Chishti, who launched an unlikely leadership bid on Sunday, appears to have none so far, while Transport Secretary Grant Shapps has the second-fewest.

Ballots are to be held this Wednesday and Thursday, and next Tuesday and Wednesday, with the candidates with the lowest number of votes eliminated and MPs re-balloted until only two candidates are left.

The bar to stay in the contest increases with the first ballot, when Mr Blackman said contenders with votes from fewer than 10% of the parliamentary party – or 36 MPs – will likely be out.

“After that we probably won’t need thresholds because the list will shorten considerably,” he said.

If, as party bosses hope, two candidates remain in the process by next Thursday, they will face a postal vote of Conservative Party members over the summer.

Mr Blackman said it is a “condition of nomination” for candidates to agree that they will contest the ballot of party members if they reach the final two.

This is to avoid a situation as in 2016, when Dame Andrea Leadsom dropped out, handing the leadership unchallenged to Theresa May before party members were given the opportunity to vote.

Environment Secretary George Eustice said the two candidates will “go out on a series of hustings around the country during August, possibly early September”, and indicated that a new leader could be in place by the “middle of September”.

A series of debates and hustings in Parliament and around the country will give the candidates a chance to try to convince MPs and party members that they should be elected leader.

Two live televised Conservative leadership debates have also been announced, one to be aired by ITV at 7pm on Sunday, and the second by Sky News on Monday.

Meanwhile, 1922 Committee vice-chairwoman Nusrat Ghani said that while there is “anxiety” about Mr Johnson staying on as Prime Minister, the “ship has sailed” on installing a caretaker premier, as some in the party have called for.

The Conservative MP told BBC Radio 4’s World At One programme: “I do get contacted by colleagues from all sides of the party and there has been disquiet that we haven’t had a situation where there was a caretaker prime minister in place.

“But I really do think that ship has sailed and I firmly think that, as the 1922, we just need to now focus on running a really smooth and efficient leadership election.”