ITV News Correspondent Romilly Weeks explains why more of Boris Johnson's support is seeping away as two more Tory MPs urge for his resignation amid criticism of a supposed lack of integrity
Boris Johnson will face a third partygate probe after MPs agreed the Privileges Committee should investigate whether he misled Parliament with his repeated denials about Downing Street parties during the coronavirus lockdown.
There was no need for the Commons to hold a vote whether to launch an investigation as the motion went through without opposition.
It was a damaging debate for Mr Johnson with several Tory MPs using their time in the Commons to call on the prime minister to resign.
Senior Tory Steve Baker said the possibility of him forgiving the PM for breaking his own coronavirus rules was "gone", adding: "The prime minister should just know the gig's up."
'Really damaging': Robert Peston breaks down how today's events show support for the PM is fractured among Tory MPs
Conservative backbencher William Wragg told MPs he "cannot reconcile" Mr Johnson remaining as prime minister as he reminded MPs that he had already submitted a letter of no confidence in the Tory leader.
He rubbished the argument that the war in Ukraine should keep the prime minister in post, saying: "The invasion of a sovereign nation by a dictatorial aggressor should not be a reason why we should accept lower standards ourselves."
Listen to the ITV News What You Need To Know podcast - with the latest on the partygate probe
Conservative MP Anthony Mangnall has said he cannot forgive the prime minister for "misleading the House".
"Every day that I see issues and rules broken in this place only reaffirms my belief that we have to stand up in this place and make it clear that dishonesty, that inaction and misleading of the House cannot be tolerated from anyone."
Labour leader Sir Keir Starmer said his motion was about the principle of "honesty, integrity and telling the truth" as he urged MPs back an investigation into the PM's conduct.
He said the PM had tried to "cover up his misdeeds" by taking advantage of the Commons convention not to call someone a liar.
"The prime minister has stood before this House and said things that are not true, safe in the knowledge that he will not be accused of lying because he can't be," Sir Keir said.
"He has stood at that despatch box and point blank denied rule-breaking took place, when it did.
"As he did so, he was hoping to gain extra protection from our good faith that no Prime Minister would deliberately mislead the House."
Labour leader Kier Starmer says Boris Johnson "must go" but it is up to his own MPs to make that happen.
Scotland Yard's investigation into the parties in Downing Street and Whitehall during England's lockdowns in 2020 and 2021 is continuing, although May 5's local elections mean no announcement about further fines will be made until after polling day.
The PM told ITV News he is "determined" to lead his party into the next general election, despite many people believing he will receive more police fines.
He is thought to have been at six of the 12 events under investigation by Scotland Yard.
The motion being voted on by MPs states Mr Johnson's comments "including but not limited to" four separate remarks in the Commons "appear to amount to misleading the House".
He said the partygate saga has gone one "for quite a long time" and "there's a limit to the amount of focus politics should have on this", but he accepted the need for an investigation.
"I want all the facts to be out there," Mr Johnson said, but partygate shouldn't "crowd out everything else".
Did the government perform another U-turn?
Late on Wednesday night it emerged that the government would be adding an amendment to the vote to delay it, but just minutes before the debate began it was pulled.
Mr Johnson said during a visit to India that MPs should wait for the police investigation to conclude so they can get the "full facts" of the partygate scandal.
But the PM agreed it was the "prerogative" of MPs to vote today whether an investigation should follow the conclusion of the police investigation and the release of Sue Gray's report.
Downing Street explained that the amendment was dropped because it had become clear that any Privileges Committee investigation would not start until MPs had seen Ms Gray's report into government partying during the pandemic.
A senior government source said Mr Johnson was "happy to face" a parliamentary inquiry after Tory MPs were granted a free vote on whether he should.
During his trip to India, the PM wanted to talk about trade, but as Deputy Political Editor Anushka Asthana reports, he could not escape questions about the partygate scandal dogging his premiership
What can the Privileges Committee do? Could Boris Johnson be expelled from Parliament?
The Privileges Committee will decide whether the PM committed contempt of Parliament by misleading the House, a charge which once upon a time could have resulted in a prison sentence.
The power to imprison - or fine - has not been used by Parliament in well over 100 years but there are some severe sanctions the Privileges Committee could recommend.
It could say Mr Johnson should be suspended from Parliament, or even expelled if it takes a critical enough view of his conduct.
If he is expelled from Parliament he would cease to be an MP, however he would not be banned from running for election again.
If he's suspended for more than two weeks he would face a recall petition which could result in him defending his seat at a by-election. If 10% of his constituency backs a recall petition it would trigger a by-election.
Any proposed sanctions would be voted on by MPs, but because of Mr Johnson's large Commons majority, they would be unlikely to go through.
Fans of Parliamentary convention would expect the PM to resign if he's found in contempt of Parliament but as prime minister he could decide that is not necessary.
Those critical of the PM say the police fine shows he did break the law and therefore misled Parliament by claiming he didn't.
Asked on the first day of his trade mission to India whether he knowingly or unknowingly misled Parliament, Mr Johnson said: "Of course not".
Under the ministerial code - which has been signed by the PM - anyone in government found to have knowingly misled MPs is "expected to resign".