Boris Johnson is on the verge of being ousted as Conservative Party leader and prime minister, after the number of Tory MPs demanding he resign reached the threshold for a vote of no confidence.

Chairman of the backbench 1922 Committee Sir Graham Brady has announced that 54 or more Tory MPs have requested a vote of confidence in the PM, triggering a leadership vote.

Tory MPs will vote this evening between 6pm and 8pm on whether they want Johnson to remain.

While plenty of Westminster insiders predict Johnson will survive the vote, the fact it has been called is damaging for the prime minister.

Brady said in a statement: “The threshold of 15 per cent 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 6pm and 8pm 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.”

Speaking to journalists, Brady suggested some MPs had post dated their letters so the vote did not overshadow the Queen’s jubilee celebrations.

It comes after former minister Jesse Norman became the latest Tory MP to announce that he has submitted a letter calling for a confidence vote in Johnson.

Norman, the MP for Hereford and South Herefordshire, said Johnson had presided over “a culture of casual law-breaking” in No.10 and that his claim to be vindicated by the Sue Gray report was “grotesque”.

In order to oust him, 180 MPs would have to vote against Johnson in the confidence vote.

However, the odds are in the PM’s favour with around 140 MPs on the “payroll” alone including ministers and aides.

Cabinet ministers have been lining up to declare their support for the prime minister.

Foreign secretary Liz Truss tweeted: “The prime minister has my 100 per cent backing in today’s vote and I strongly encourage colleagues to support him.

“He has delivered on covid recovery and supporting Ukraine in the face of Russian aggression. He has apologised for mistakes made. We must now focus on economic growth.”

Levelling up secretary Michael Gove added: “I’ll be voting for Boris this evening. The PM got the big decisions right on Brexit and Covid.

“We need to focus now on defending Ukraine, driving levelling-up and generating growth. We need to move past this moment and unite behind Boris to meet these challenges.”

Conservative MP Michael Fabricant said he thinks Johnson will win the vote no of confidence on Monday evening.

He told Times Radio: “I think he is going to win. I think that something like two-thirds of the party will vote to support him and I really do wonder why it’s happening at this time.”

A No.10 spokesperson said:“Tonight is a chance to end months of speculation and allow the government to draw a line and move on, delivering on the people’s priorities.

“The PM welcomes the opportunity to make his case to MPs and will remind them that when they’re united and focused on the issues that matter to voters there is no more formidable political force.”