Boris Johnson could face a parliamentary misconduct investigation if MPs back a crunch House of Commons motion over his breaches of coronavirus laws.
The motion, put forward by Labour, would refer the Partygate saga to the privileges committee - which can determine whether the Prime Minister's repeated denials of there being any parties in Number 10 during lockdown amounted to a "contempt of the House". By convention, if a Government minister is found to have misled Parliament they are expected to resign or are usually sacked.
Labour leader Keir Starmer, speaking ahead of Thursday's vote, said: "We are urging Conservative MPs to do the right thing. To respect the sacrifices that their constituents made during the pandemic.
Read more: Energy bosses warn some customers could be paying £1 in every £6 on bills by October
"To say that the public were right to follow the rules. And to vote in the national interest not under pressure from the party whips.
“The British public know that the rules were broken in Downing Street.
"Voting to say otherwise won’t persuade the public that everything was fine but will further damage the reputation of any Conservative MP who is happy to say it was one rule for the public and another for this Government. Tomorrow’s vote is an important step to restoring decency, honesty and integrity into our politics.”
At Prime Minister's Questions, Sir Keir focused again on the Partygate scandal, asking: "Does the Prime Minister actually accept that he broke the law?”
Mr Johnson replied: “Yes, Mr Speaker I’ve been absolutely clear that I humbly accept what the police have said, I paid the fixed penalty notice, and what I think the country and what I think the whole House would really rather do, is get on with the things for which we were elected, deliver on our promises to the British people."
Do you think Boris Johnson should stay on as Prime Minister? Have your say in the comments
Blaydon MP Liz Twist, speaking during the exchanges, said: "My constituents are angry that while they stuck to the law, the Prime Minister broke it.
"Trust in his government is broke. So when will he go?"
Mr Johnson said he had "apologised heartily" for the Covid breaches in Number 10, adding: "All I can do is renew and repeat the apologies I have given to her constituents, whether they accept them or not."