Boris Johnson has responded to a questionnaire from the Metropolitan Police about Downing Street gatherings during coronavirus restrictions.
A Number 10 spokesperson confirmed to Sky News that the prime minister has returned the document.
Mr Johnson had seven days to respond to the questionnaire, which was sent to him last Friday.
Questionnaire has legal status
The document, which has been sent to all those believed to have attended alleged COVID-19 lockdown-busting parties, asks for the recipient’s account and an explanation of their participation in an event.
Scotland Yard has stated the questionnaire has formal legal status and must be answered truthfully.
The force has been contacting more than 50 people believed to have been involved in the 12 events it is investigating as part of Operation Hillman.
RAF plane flew hundreds of miles for Boris Johnson photoshoot before flying back
‘Forging a new partnership’: UK and Australia agree £25m security package
Russia-Ukraine crisis: Boris Johnson says Russia sending ‘mixed signals’ as Moscow says West ‘humiliated’ over Ukraine invasion warnings
The Met has said those contacted will not necessarily be given a fine.
But a statement earlier this month said: “Nevertheless, if following an investigation, officers believe it is appropriate because the COVID regulations have been breached without a reasonable excuse, a fixed penalty notice will normally be issued.”
How did we get here?
Allegations of lockdown-busting events in Downing Street and across Whitehall in 2020 and 2021 have piled pressure on the PM, with some of his own backbench MPs joining opposition parties in calling on Mr Johnson to go over the row.
A partial version of a Cabinet Office inquiry into the claims, led by senior civil servant Sue Gray, said Downing Street lockdown gatherings represented a “serious failure” and were “difficult to justify”.
In the wake of the highly-critical report, which looked at 16 gatherings, the Met announced it would be investigating a dozen of those events for potential breaches of COVID regulations.
These include an event that happened at the Downing Street flat on 13 November 2020, the night aides Dominic Cummings and Lee Cain left their Number 10 roles, and an event to mark the PM’s birthday on 19 June 2020.
Last week, a fresh photo emerged of Mr Johnson at a Christmas quiz in Number 10, an event that police initially decided not to investigate.
But the Met is now rethinking its assessment of that event following the publication of the image of the PM next to an opened bottle of alcohol, crisps, a person wearing tinsel and another wearing a Santa hat.
Ms Gray has handed more than 300 images and more than 500 pages of information to Scotland Yard.
How much trouble is the PM in?
A total of 14 Tory MPs have so far called for Mr Johnson to resign, but the momentum behind the internal party pressure for the PM to go has waned in recent weeks.
Many MPs are thought to be waiting for the outcome of the police investigation into partygate.
If Mr Johnson is fined, this would likely provoke a fresh wave of calls for him to go.
The PM has so far dismissed the notion of resigning over the row, meaning Conservative critics will have to force a no-confidence vote in his leadership of the party.
A total of 54 letters – from 15% of the party’s 360 MPs – are needed to trigger a leadership vote.
If Mr Johnson were to win such a ballot, he would be immune from another leadership challenge for a year.
Were he to lose, he would have to resign and a successor as party leader and PM would be chosen.