Sue Gray has been stuck in last minute talks about her final draft of the report, which could determine Boris Johnson's future as Prime Minister.
Sue Gray - who is a senior civil servant - is leading a probe into allegations that parties took place at Downing Street when the rest of England was in lockdown.
According to reports, she has spent hours going through her completed report with top officials, Met police and Government lawyers.
The inquiry chief wants the report to be published in full so needs their sign off before sending it to the Prime Minister, The Mirror reports.
It means Mr Johnson’s leadership is still hanging in the balance - with No 10 anxiously awaiting the contents of the final draft.
It could even be delayed until next week, raising the prospect of already mutinous Tory MPs encouraged to take action by angry constituents this weekend.
The PM also faces being interviewed by police after Scotland Yard said Downing Street parties crossed the threshold for investigation.
But the Mirror can also reveal that Mr Johnson’s chief of staff, Dan Rosenfield, downplayed down the severity of the police probe in a meeting of Government advisors on Tuesday night.
“At worst it will be like getting a fixed penalty fine for speeding, nothing to worry about,” he told them.
During a rowdy PMQs, Mr Johnson rejected calls to quit as he waited anxiously for the official report into the ‘partygate’ row.
The PM insisted he was “getting on with the job”, although he acknowledged there were people who “want me out of the way” for a variety of reasons.
He and his allies have been speaking to dozens of Tory MPs in his Commons office over the last 24 hours in an attempt to shore up his position.
Labour leader Keir Starmer accused the PM of showing “nothing but contempt” for the public over lockdown parties.
The ex-Director of Public Prosecutions blasted: “If he misled Parliament, he must resign.”
But pressed on whether he would now quit, Mr Johnson said: “No.”
Mr Starmer said: “We now have the shameful spectacle of a Prime Minister of the United Kingdom being subject to a police investigation, unable to lead the country, incapable of doing the right thing and every day his Cabinet fail to speak out they become more and more complicit.”
The Government had “shown nothing but contempt for the decency, honesty and respect that define this country”, he added.
Mr Johnson replied: “Of course he wants me out of the way - he does, and of course I don’t deny, for all sorts of reasons, many people may want me out of the way.”
An indication of how damaging the Gray report could be for the Government came when Scotland Yard chief Dame Cressida Dick announced a police inquiry was being carried out.
Downing Street has previously said the report will be published in full - and sources close to the Gray inquiry said that was their expectation.
But ultimately it is a matter for Mr Johnson to decide - and No 10 would only say it was its “intention” to publish the report.
However, any attempt to hold back parts of it would be met by a barrage of criticism.
Foreign Secretary Liz Truss, tipped as a leading candidate to succeed Mr Johnson, said: “He’s admitted that mistakes were made and I 100% support him, and want him to continue as Prime Minister.”
She claimed there could be “security issues” which mean parts of the Gray report are “problematic to publish”.
But she stressed: “We have been absolutely clear that we will publish the findings of the report.”
The steady stream of allegations over alleged breaches of lockdown rules have rocked No 10.
Many of the PM’s critics, from all wings and generations of the Tory party, are waiting for Ms Gray’s report before deciding whether or not to submit formal letters to trigger a confidence vote.
In a warning to wavering rebels, Commons Leader Jacob Rees-Mogg suggested there would have to be a general election if Mr Johnson is ousted.
However, neither John Major, Gordon Brown nor Theresa May called one when they took over in No 10 mid-term.
