It is understood the report - compiled by senior civil servant Sue Gray - will not be made public until "in all likelihood next week", when MPs return to the Commons after the weekend.

The version made public will be redacted to ensure it is compliant with the Metropolitan Police's earlier request that nothing jeopardises their inquiry, it is believed.

Reaction as police issue second statement on partygate report - politics live

It comes as the Met said on Friday evening that it had received the information requested to support its investigation into alleged COVID rule-breaking in Westminster.

Commander Catherine Roper said: "We have not delayed this report and the timing of its release is a matter for the Cabinet Office inquiry team."

She said the Special Enquiry Team, which is leading the investigation, was examining the Cabinet Office material "to establish whether individuals attending the events in question may have breached the regulations".

Earlier in the day, police had earlier called for "minimal reference" in Sue Gray's report to the events it is investigating - raising new doubts over when it would be published.

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When the police investigation into partygate began on Tuesday, the force told journalists it did not believe the full publication of the report would prejudice its own investigation.

But the first statement issued by the force today 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."

PM to receive redacted version of Gray report

Lawyers have questioned the Met's request, with one describing it as "absolute nonsense".

But in the force's the latest statement, Ms Roper explained further the earlier remarks.

"In order to protect the integrity of the police investigation, as is appropriate in any case, and to be as fair as possible to those who are subject to it, the Met has asked for minimal reference to be made in the Cabinet Office report to the relevant events," she said.

"This will only be necessary until these matters are concluded and is to give detectives the most reliable picture of what happened at these events. We intend to complete our investigations promptly, fairly and proportionately."

Her statement continued: "The offences under investigation, where proven, would normally result in the issuing of a fixed penalty notice; accordingly our investigative actions will be proportionate to the nature of these offences."

It adds that "where there is sufficient evidence that individuals have breached the regulations without reasonable excuse, officers will decide if enforcement action is appropriate" and fixed penalty notices will be issued.

The Met announced earlier this week it was investigating a "number of" gatherings in 2020 and 2021 for potential breaches of coronavirus rules.

Lawyers question Met's request

Some have questioned how the Met's investigation can be prejudiced if only lesser offences are being considered.

Publication of reports and other inquiries can often be delayed until a police investigation and any court case is concluded, typically to avoid the risk of prejudicing a jury.

However, if police investigate under coronavirus laws there would be little risk of prejudice as the penalty for breaking lockdown rules is a fine and it is highly unlikely to result in a prosecution.

Nazir Afzal, a former chief prosecutor for the North West, tweeted: "This is absolute nonsense from the Met Police.

"A purely factual report by Sue Gray cannot possibly prejudice a police investigation. They just have to follow the evidence, of which the report will be a part."

Meanwhile, former director of public prosecutions, Lord Macdonald, suggested to the BBC the Met's stance was "disproportionate".

Repot not yet with Number 10

Ms Gray's report, which is likely to have a significant impact on Mr Johnson's future as prime minister, has not yet been delivered to Number 10.

Sir Keir Starmer, the Labour leader, said he wanted the report "in full and the investigation finished as quickly as possible", claiming the government is "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," said Sir Keir.

Downing Street has said it has not asked Ms Gray to go back to the Met to make sure her report doesn't interfere with the police investigation.

A spokesman insisted it was "an independent investigation" and that the Met's announcement on Friday had no involvement from Number 10.