Boris Johnson has received the long-awaited report by Sue Gray into lockdown parties in Downing Street and Whitehall.
The senior civil servant’s findings are expected to be made public within hours.
The prime minister is then likely to make a statement in the House of Commons which would be followed by questions from MPs.
The extent of the detail contained in the report will be the subject of intense scrutiny, following a request from the Metropolitan Police that it make only “minimal reference” to events are being looked at as part of its criminal probe.
Last week Cabinet Office sources confirmed Ms Gray would follow that request.
Although the prime minister has committed to publishing the report in full, opposition parties fear redactions could mean the details of the most serious breaches will never be made public.
Sir Keir Starmer, the Labour leader, recently said he wanted the report published “in full and the investigation finished as quickly as possible”, claiming the government was “paralysed” by the police probe.
“Any issues of prejudice have got to be worked through but this whole mess, this whole paralysing of politics, is being caused by the prime minister and his wrongdoing,” he said.
Mr Johnson has come under pressure to resign over the partygate revelations concerning gatherings that took place in Downing Street and across Whitehall in 2020 and 2021 when COVID-19 restrictions were in place.
If the Cabinet Office report is critical of the PM – particularly if the findings indicate he may have misled parlaiment – it could further imperil his position and spark a no-confidence vote in his leadership if enough of his Conservative MPs demand a contest.