The Sue Gray report into parties in Downing Street and Whitehall that may have broken COVID rules could be published as soon as tomorrow, according to a government source.

Downing Street has said discussions are still ongoing between the officials involved with the investigation by the senior civil servant and the Metropolitan Police, which announced today it would be launching a criminal probe.

It is understood Number 10 has yet to receive a copy of the report.

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Once it is received it could be published within hours. The prime minister has vowed to make a statement and answer questions in the House of Commons after its publication.

Earlier it had been suggested the publication of the Gray report would be delayed until the police investigation concludes.

But Sky News understands Scotland Yard made clear to government officials it did not believe the findings would prejudice its investigation.

The report is likely to provide a factual account of what happened at a number of alleged parties, and may present a judgement on whether the events breached rules in place at the time.

Earlier this month Boris Johnson issued an apology in the House of Commons for attending an event in the Number 10 garden on 20 May 2020, claiming he thought it was a “work event”, and asked people to wait for Ms Gray to publish her findings.

Opposition parties and some critics on his own backbenches say any evidence he has misled parliament would amount to a breach of the ministerial code and require the prime minister’s resignation.

Mr Johnson’s leadership is under severe pressure and could be put to a vote if more than 54 Conservative MPs submit letters of no confidence to the chairman of the 1922 Committee of backbench MPs.