Boris Johnson faces more questions about No 10 parties from MPs later, as the results of an internal inquiry into possible lockdown breaches are due.
It is understood the highly-anticipated report, by senior official Sue Gray, is largely complete and could be published as early as Wednesday.
But it is not expected to be revealed ahead of Prime Minister’s Questions at noon.
It comes after the Met Police announced its own investigation on Tuesday.
Commissioner Cressida Dick said the force was looking into potential breaches of Covid laws at a number of events in government buildings since 2020.
The police probe heaps further pressure on the PM, after weeks of headlines about gatherings in Downing Street when laws preventing social mixing were in place.
The PM has apologised for attending a “bring your own booze” event on 20 May 2020, during the first lockdown, saying he thought it was a “work event”.
Fresh allegations of a birthday party being held for the prime minister in June 2020 have also come to light.
Some Conservative MPs have called openly for Mr Johnson to resign over the party allegations – but ministers have urged others to wait for Ms Gray’s findings.
Many Tories are waiting on her report before deciding whether to submit letters of no confidence in Mr Johnson, potentially triggering a leadership contest.
At least 54 must write to Sir Graham Brady, chairman of the backbench 1922 Committee, to set up a vote of confidence in the prime minister.
Mr Johnson has already pledged to make a statement in the Commons after the report is made public. There has been no official confirmation of when it will be published.
Labour has urged the government to give MPs enough time to digest the report before any statement, with copies issued well in advance.
Speaking to BBC Newsnight, Leader of the Commons Jacob Rees-Mogg said: “The government will behave entirely properly in terms of any statement, and the usual courtesies are extended to the opposition.”
He said the cabinet was in “unanimous support” of the prime minister, because “anyone who did not support the prime minister would be obligated to resign”.
Also speaking to BBC Newsnight, shadow attorney general Emily Thornberry said the prime minister’s attitude towards the allegations of parties during lockdown had undermined his authority.
Ms Thornberry said Boris Johnson “knew all along that he had been involved in many, many parties” and had “covered up and kept covering up”.
She added that “he doesn’t have the authority to lead” on issues such as the cost of living crisis or Russian threats to Ukraine.