Sue Gray’s long-awaited report on allegations of lockdown-breaching parties at 10 Downing Street could be on Boris Johnson’s desk as early as this evening.

The Whitehall mandarin has completed her investigation and is only awaiting clearance from the police to hand over the potentially explosive document. Downing Street has said the prime minister wants to publish it – in full or in part- “as soon as possible”, meaning its findings may be known by Wednesday.

Plans to bring the inquiry to a swift conclusion this week were thrown into chaos today by the bombshell announcement by Metropolitan Police Commissioner Cressida Dick that the force is to mount its own inquiry into possible criminal offences.

Downing Street initially announced that this development would delay Ms Gray’s report, telling reporters that she would be unable to publish information relating to alleged parties which are covered by the police probe.

Instead, she would be able to release only a partial summary of those events in Downing Street and government departments not deemed by police to merit criminal investigation.

Whitehall sources said the announcement caused “complete confusion” in the Cabinet Office, where Ms Gray’s investigation is based at arm’s length from No 10.

And it seems to have caught the Met off guard, with the force briefing that it was not demanding any delay in publication.

Ms Gray’s team contacted police counterparts for confirmation, and the two sides were on Tuesday afternoon locked in discussions about what elements of the report can or cannot be made public.