Mr Johnson is 2/5 to win the looming vote of no confidence into his leadership. But bookmakers still expect the Prime Minister to leave Downing Street by the end of the year.
Jeremy Hunt is the 9/2 favourite to replace Mr Johnson as Tory leader, while Liz Truss is 7/1 to succeed him.
Mr Hunt today said he would vote against the PM, warning that the Tories will lose the next election if Mr Johnson remains in post.
The former Foreign Secretary said: “Having been trusted with power, Conservative MPs know in our hearts we are not giving the British people the leadership they deserve.
“We are not offering the integrity, competence and vision necessary to unleash the enormous potential of our country.
“And because we are no longer trusted by the electorate, who know this too, we are set to lose the next general election.
“Anyone who believes our country is stronger, fairer and more prosperous when led by Conservatives should reflect that the consequence of not changing will be to hand the country to others who do not share those values.
“Today’s decision is change or lose. I will be voting for change.”
The Betfair Exchange puts Tom Tugendhat at 8/1, Penny Mordaunt at 8/1, Rishi Sunak at 9/1, Ben Wallace at 12/1, Nadhim Zahawi at 17/1 and Sajid Javid at 19/1.
Betfair spokesperson Sam Rosbottom said: “Boris Johnson will face a vote of no confidence from his Conservative MPs today after the motion was triggered this morning.
"The Prime Minister, who was booed during a service for the Queen’s Platinum Jubilee on the weekend, is 2/5 to win, like his predecessor Theresa May did in 2018.
"However, he is odds-on at 5/6 on Betfair Exchange to leave No.10 this year.
“Jeremy Hunt is the 9/2 to replace Mr Johnson with Liz Truss 7/1 and Tom Tugendhat 8/1.”
It comes after Sir Graham Brady, chairman of the backbench 1922 Committee, confirmed in a statement that he has now received the 54 letters from Conservative MPs needed to trigger a vote.
The vote – by secret ballot – will take place at Westminster on Monday between 6pm and 8pm, with the count to take place immediately afterwards.
To oust the Prime Minister, the rebels will need 180 MPs – and allies of Mr Johnson made clear he is determined to fight to stay on.
Sir Graham said in a statement: “The threshold of 15 percent of the parliamentary party seeking a vote of confidence in the leader of the Conservative Party has been exceeded.
“In accordance with the rules, a ballot will be held between 1800 and 2000 today Monday June 6 — details to be confirmed.
“The votes will be counted immediately afterwards. "An announcement will be made at a time to be advised. Arrangements for the announcement will be released later today.”
Boris Johnson and Jeremy Hunt PA
Jeremy Hunt stood for the leadership in 2019 Stefan Rousseau