Members of the powerful 1922 Committee executive, which will decide the timetable for a leadership election, want his successor in Downing Street by 5 September.

"We expect the new prime minister to be elected in time for the September session," a senior Conservative MP familiar with the process told Sky News.

Politics latest: Starmer gives statement after 'beergate' verdict as new favourite to be next PM emerges

The Commons is due to rise for the summer recess in just under two weeks, on 21 July, and MPs will return to Westminster for three weeks on 5 September, ahead of the autumn party conferences.

The 1922 Committee, led by veteran Tory MP Sir Graham Brady, is set to defy a call by former prime minister Sir John Major for Mr Johnson to be removed now, with a caretaker PM stepping in.

But executive members of "the '22" - known in Westminster folklore as "the men in grey suits" - are opposed to Mr Johnson's wish to stay in office until the Tory conference in early October.

"The expectation is that we will be down to two candidates before we go into recess," the senior MP added. "Therefore, that means Boris Johnson has two more PMQs (prime minister's questions) only."

Those two sessions, likely to see a defiant Mr Johnson come out fighting against opposition MPs and his enemies on the Tory benches, will be next Wednesday, 13 July, and a week later, 20 July.

The proposed timetable means Mr Johnson may also have attended his last international gatherings with world leaders when he took part in the Commonwealth, G7 and Nato summits late last month.

Read more: Who are the frontrunners to be the next PM?

Asked if Mr Johnson would attend the United Nations general assembly in New York, which opens on Tuesday 13 September, the PM's official spokesman said: "It's up to the 1922 Committee."

It has also emerged that a wedding party at Chequers during the summer planned by Mr Johnson and wife Carrie, which critics claimed was one reason why he wanted to cling to power, will now take place at a different venue.

Tory MPs will elect a new executive of the 1922 Committee on Monday, but the current executive met just hours after Mr Johnson's Downing Street resignation announcement and no changes to current thinking are expected.

An announcement of the timetable for the leadership election will be made after executive elections on Monday and nominations are likely to open on Tuesday and early rounds of voting by MPs are expected later next week.

Under the rules, the bottom candidate drops out after each round of voting by MPs until just two are left and 100,000 party members then choose the new leader and the country's next prime minister.

Nomination change urged 'to exclude no-hopers'

There is some concern among senior MPs, however, about the number of candidates declaring that they may enter the contest.

Some MPs believe the number of candidates could be 10 or even 12.

As well as the acknowledged frontrunners, such as Ben Wallace, Liz Truss, Tom Tugendhat, Suella Braverman, Rishi Sunak, Nadhim Zahawi and possibly Sajid Javid and Grant Shapps, some low-profile backbenchers have suggested they may stand.

While senior backbencher and leading Brexiteer Steve Baker is a high-profile figure, relatively unknown MPs John Baron and Rehman Chishti have suggested they may run, to the dismay of MPs who want a swift contest.

One key decision for the next 1922 executive will be the number of nominations required to get on the ballot paper.

It is currently eight, but some Tory MPs want it raised to as high as 20, to exclude no-hopers.