Boris Johnson is facing a vote of no confidence by Tory MPs amid anger across the party at the disclosures over lockdown parties in Downing Street.

Sir Graham Brady, the 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.

It comes after a steady stream of Tory MPs called publicly for the Prime Minister to stand down in the wake of Sue Gray’s report into breaches of the Covid regulations in No 10 and Whitehall.

In order to oust the Prime Minister however the rebels will need 180 MPs, and allies of Mr Johnson made clear he is determined to fight to stay on.

Speaking shortly after Sir Graham made his announcement, Health Secretary Sajid Javid told Sky News: “If there is (a vote) the Prime Minister will stand and fight his corner with a very, very strong case.”

The Prime Minister will stand and fight his corner with a very, very strong case

Sir Graham said he had informed Mr Johnson on Sunday that the threshold of 15% of the parliamentary party calling for a vote had been passed.

“I have followed the rules that we have in place. I notified the Prime Minister yesterday and we agreed the timetable for the confidence vote to take place,” he said.

“He shared my view, which is also in line with the rules that we have in place, that that vote should happen as soon as it could reasonably take place and that would be today.”

A No 10 spokeswoman 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.”

Earlier, former minister Jesse Norman became the latest Tory MP to go public with his call for Mr Johnson to go.

In a scathing letter posted on social media, he said the Prime Minister had presided over “a culture of casual law-breaking” in No 10 and that his claim to be vindicated by Ms Gray’s report was “grotesque”.

He said the Government’s current priorities were “deeply questionable”, its policy of offshoring the processing of asylum claims to Rwanda was “ugly”, while any breach of the Northern Ireland Protocol would be “politically foolhardy and almost certainly illegal”.

“Neither the Conservative party nor this country can afford to squander the next two years adrift and distracted by endless debate about you and your leadership,” he said.

“For you to prolong this charade by remaining in office not only insults the electorate, and the tens of thousands of people who support, volunteer, represent and campaign for our party; it makes a decisive change of government at the next election much more likely. That is potentially catastrophic for this country.”