Boris Johnson may have misled parliament on multiple occasions over whether lockdown rules were broken in Downing Street, MPs have found.
If found guilty, the former prime minister could be suspended or expelled from the Commons and even trigger a by-election in his seat.
In a damning report published on Friday, the Commons privileges committee said the breaches by No.10 staff “would have been obvious” to Johnson.
“There is evidence that the House of Commons may have been misled.” the MPs said, listing four separate occasions.
Johnson is due to defend himself in front of the committee in person later this month.
The committee is not investigating whether rules were broken or not, the police have already concluded they were, but specifically whether Johnson lied to parliament about it.
As prime minister, Johnson repeatedly told the Commons that no Covid rules had been breached in No.10. But he was later fined by police for attending a birthday party thrown for him in the Cabinet Room.
The MPs said: “The evidence strongly suggests that breaches of guidance would have been obvious to Johnson at the time he was at the gatherings.
“There is evidence that those who were advising Johnson about what to say to the press and in the House were themselves struggling to contend that some gatherings were within the rules.”
The 24-page report goes on to say: “It appears that Mr Johnson did not correct the statements that he repeatedly made and did not use the well-established procedures of the House to correct something that is wrong at the earliest opportunity.”
The committee also said there was evidence “a culture of drinking in the workplace in some parts of No.10” continued “after Covid restrictions began”.
Today’s report is not the committee’s final conclusion, but if it decides Johnson did mislead parliament it can recommend punishments such as suspension or expulsion from the Commons, which MPs would then have to vote on.
Angela Rayner, Labour’s deputy leader, said: The evidence in this report is absolutely damning on the conduct of Boris Johnson, not just in the crime but the cover up.
“All the while, Rishi Sunak sat on his hands, living and working next door but doing nothing to end the rule breaking.”
Rayner said if Johnson is found to have misled parliament, Sunak must make clear “his career is over”.
In his response, Johnson insisted his version of events had been “vindicated” by the report.
He then turned his fire on Sue Gray, the senior civil servant who published her own damning report into partygate and is about to become Keir Starmer’s chief of staff.
Johnson said: “I note that the committee has emphasised their wish to be fair.
“They have made reference on new fewer than 26 occasions to a personage they bashfully describe as ‘the Second Permanent Secretary to the Cabinet Office’. That is of course, Sue Gray.
“So it is surreal to discover that the committee proposes to rely on evidence culled and orchestrated by Sue Gray, who has just been appointed chief of staff to the leader of the Labour Party.”
However, the committee - which has a Tory majority - responded: “The committee’s report is not based on the Sue Gray report.
“The committee’s report is based on evidence in the form of material supplied by the government to the committee in November, including communications such as WhatsApps, emails and photographs from the official Downing Street photographer; evidence from witnesses who were present either at the time of the gatherings or at the time of preparation for Boris Johnson’s statements to parliament.
“Sue Gray was present at neither and is not one of those witnesses.”