Boris Johnson has warned his MPs not to "gratify our opponents by turning in on ourselves” ahead of a vote of no confidence in his leadership.
The PM faces the test of his leadership on Monday evening after the threshold of at least 54 Conservative MPs wrote to Sir Graham Brady, chairman of the 1922 Committee, saying they no longer have confidence in their leader.
The vote will take place in the House of Commons between 6pm and 8pm and the result will be made public at 9pm.
At least 180 Tory MPs will need to turn on their leader for him to be removed.
Johnson addressed Tory MPs in a private meeting in Westminster in a last-ditch attempt to shore up support.
A senior party source said the prime minister received five questions during the meeting, two of which were “hostile” and three of which were not.
The PM told the 1922 Committee “I will lead you to victory again”, warning against descending into a “pointless fratricidal debate” about the future of the Conservative Party, one source revealed.
He told the private meeting: “I humbly submit to you that this is not the moment for a leisurely and entirely unforced domestic political drama and months and months of vacillation from the UK.”
Watch: Boris Johnson to face confidence vote as rebel Tories mount leadership challenge
At least 145 MPs have publicly indicated support for him, according to a tally by the Reuters news agency.
The prime minister has been teetering on the edge of a vote for some weeks, sparked in main by the Partygate scandal that saw the PM fined for attending a party in Downing Street, while the UK was subject to stringent lockdown rules.
Despite issuing a grovelling apology following the publication of the damning Sue Gray report, Johnson has not managed to secure the support of enough of his own party to stave off a vote.
Polling in recent weeks has also made desperate reading in terms of Johnson's personal popularity.
This was most publicly demonstrated on Friday when he was booed by a significant section of the crowd during his arrival at a thanksgiving service for the Queen's Platinum Jubilee at St Paul’s Cathedral.
Downing Street said Johnson “welcomes the opportunity to make his case to MPs”, with a No 10 spokeswoman adding that Monday night’s secret ballot was “a chance to end months of speculation and allow the Government to draw a line and move on”.
A number of MPs have already expressed public support for Johnson including multiple ministers such as Rishi Sunak, Sajid Javid, Dominic Raab, Michael Gove and Nadine Dorries.
However, the criticism from the many backbenchers who have criticised his leadership skills and policy priorities has been stark.
On Monday, shortly before the no-confidence vote was confirmed, a long-standing ally of 15 years issued a devastating letter of criticism.
Former Treasury minister Jesse Norman described some of Johnson's high-profile policies as “deeply questionable” and said there were no circumstances in which he could serve in a government led by him.
In his letter to the PM, Norman warned that any breach of the Northern Irish protocol would be “economically very damaging, politically foolhardy and almost certainly illegal”.
“You are the leader of the Conservative and Unionist party, yet you are putting the Union itself gravely at risk,” he said.
He said the government’s Rwanda policy was “ugly, likely to be counterproductive and of doubtful legality” and that plans to privatise Channel 4 were “unnecessary and provocative”.
In an effort to rally support for the PM, Tory MPs were sent a 12 point pamphlet trying to get MPs on side.
What happens next?
At least 50% of Tory MPs must vote “no confidence” for the prime minister to lose.
Even if Johnson survives the vote on Monday evening, his leadership could be fatally undermined if a significant number of MPs vote against him.
If Johnson is voted out or forced to resign, a leadership contest to replace him as the head of the Tory Party would take place – although he is likely to remain in post as PM until a successor has been named.
The contest takes place in two stages.
In the first stage, Conservative MPs put themselves forward as candidates.
All Tory MPs then vote in a series of rounds to reduce the number of candidates until only two remain.
The second stage of the contest sees the two remaining candidates put to a vote of Conservative Party members.