Keir Starmer's ultimatum: Go now Boris, or I'll bring a no confidence vote in Parliament

Sir Keir Starmer has said he will bring a vote of no confidence against Boris Johnson in Parliament unless the Prime Minister leaves office immediately.

The Prime Minister has announced his resignation - but said he will remain in Downing Street until a new Conservative Party leader is chosen, which could take a number of months.

No10 sources have said Mr Johnson hopes to remain in post until October, as Tory MPs and party members vote on his replacement. The official timetable of the leadership race will be announced next week.

Speaking on Thursday morning before the resignation speech, Sir Keir said Labour would bring a motion of no confidence against Mr Johnson in the Commons to force his resignation or a general election unless he stood down earlier.

“He needs to go completely,” the Labour leader said. “None of this nonsense about clinging on for a few months. He’s inflicted lies, fraud and chaos in the country.

“We’re stuck with a government which isn’t functioning in the middle of a cost-of-living crisis. And all of those that have been propping him up should be utterly ashamed of themselves.”

He added: "If they don't get rid of him then Labour will step up in the national interest and bring a vote of no confidence because we can't go on with this Prime Minister clinging on for months and months to come."

Parliamentary convention says that a Government that cannot command the confidence of MPs should either resign or go to the country in a general election.

Governments generally accept a confidence vote in the Commons within days of a call for one by the Leader of the Opposition.

The last successful no confidence vote in Parliament forced James Callaghan from office in the “Winter of Discontent” of 1979, ushering in Margaret Thatcher’s 11-year premiership.

On Thursday several Tory MPs, such as Nick Gibb, below, agreed with Sir Keir that Mr Johnson should not remain in office while the leadership contest takes place, and called for his immediate resignation and replacement with a “caretaker” leader.

Nus Ghani, a Conservative MP who sits on the executive of the 1922 Committee, said Dominic Raab, the deputy prime minister, should take over in the meantime.

Aaron Bell, a rebel who has called for Mr Johnson’s resignation for some weeks, said: "I think it would be better for the country if we had a caretaker prime minister.

"He has lost the confidence of the party, that's absolutely apparent, and therefore it's not appropriate that we have anything other than a proper caretaker administration."

Between 2015 and February of this year, the Fixed-term Parliaments Act stated that a successful vote of no confidence in the Commons would lead to a 14-day period where Downing Street must command a majority or call an election.

But the Act has now been repealed, meaning that the outcome of the vote now relies on parliamentary convention.

It is likely that in a confidence vote, many Tory MPs would vote for Mr Johnson to remain in post during the leadership race to avoid a general election while the Conservatives are behind in the opinion polls.

Speaking in front of Downing Street on Thursday lunchtime, Mr Johnson said he regretted being forced from office by his party but blamed a “herd” mentality in Westminster.

"In the last few days, I tried to persuade my colleagues that it would be eccentric to change governments when we're delivering so much and when we have such a vast mandate and when we're actually only a handful of points behind in the polls, even in midterm after quite a few months of pretty relentless sledging and when the economic scene is so difficult domestically and internationally,” he said.

"I regret not to have been successful in those arguments and of course it's painful not to be able to see through so many ideas and projects myself.

"But as we've seen, at Westminster the herd instinct is powerful, when the herd moves, it moves.

"And my friends in politics, no one is remotely indispensable and our brilliant and Darwinian system will produce another leader, equally committed to taking this country forward through tough times."