Sue Gray plans to send a cut-back version of her report to Downing Street “shortly” after lengthy talks with the Met Police concluded, the Mirror understands.
The report is expected to be sent to No10 in the coming hours or days after Ms Gray handed over evidence of possible lockdown breaches to Scotland Yard.
No10 will then decide when to publish it, with the government previously suggesting this would happen when Parliament is sitting - which is next on Monday.
However, the report is set to follow the Met Police request to include only “minimal reference” to Downing Street parties the force is investigating.
It is unclear if or when a fuller report with all the details will be published, after the Met finishes its investigation.
The Metropolitan Police asked the top civil servant to make "minimal references" to the parties it is investigating in her report to avoid prejudicing its inquiry.
Scotland Yard is looking at "a number of events" in Downing Street and Whitehall during the pandemic - but the force has not specified which ones.
Reports have suggested it could be as many as eight gatherings.
At the same time, Sue Gray's report had been expected this week but the timing has been thrown into chaos by the Met's bombshell announcement of a police probe on Tuesday.
The Whitehall inquiry is understood to be still ongoing but Ms Gray may be forced to decide whether to delay her report or strip out key details.
Opposition MPs blasted the appearance of an "establishment stitch-up" and a "Whitehall whitewash", which could buy Boris Johnson a reprieve.
The Prime Minister will spend the weekend at his Chequers retreat as he seeks to shore up his battered leadership.
In a statement on Friday, Scotland Yard said: "For the events the Met is investigating, we asked for minimal reference to be made in the Cabinet Office report.
"The Met did not ask for any limitations on other events in the report, or for the report to be delayed, but we have had ongoing contact with the Cabinet Office, including on the content of the report, to avoid any prejudice to our investigation."
However some legal figures questioned why publishing the Whitehall report would prejudice the police investigation.
