The comments from Number 10 come after the Metropolitan Police announced it was launching an investigation into a "number of" gatherings during COVID-19 restrictions in 2020 and 2021, putting more pressure on the prime minister.

Speaking in the Commons, Mr Johnson told MPs: "I welcome the Met's decision to conduct its own investigation because I believe this will help to give the public the clarity it needs and help to draw a line under matters."

Live reaction and fallout as police investigation launched - politics latest

Facing questions from journalists at a regular Westminster briefing, Mr Johnson's spokesman said the PM thinks it is "entirely right for the police to investigate these matters" and "anyone asked to will co-operate fully, as you would expect".

"The PM fully acknowledges the public's anger and concern about what has been reported, he has taken responsibility for his judgments made and it is right the Met should be now given the time and space to undertake their investigations," the spokesman said.

Asked if the PM thinks he has broken the law, the spokesman replied: "I need to be cautious about what I say but I think that's fair to say that he does not."

The spokesman also revealed that the PM did not discuss the investigation with his cabinet, despite having been made aware of the force's announcement before the meeting began.

Labour: PM has become a 'national distraction'

A Cabinet Office spokesperson said its inquiry - led by senior civil servant Sue Gray - "is continuing" and there is "ongoing contact" with the Met.

Sky News understands Ms Gray's report will not be published while the Met's investigation is ongoing, but Downing Street has suggested that she is able to publish aspects of her report that do not concern matters being investigated by police.

Sources have told deputy political editor Sam Coates that police want the whole report to be published, including the accompanying evidence, and have not raised any objection to it being released during their investigation.

Labour's deputy leader Angela Rayner said Boris Johnson had become a "national distraction" and should resign.

Conservative MP David Davis, who last week called on the PM to go, said "this nightmare gets even worse", while fellow Tory Tobias Ellwood told Sky News: "I think that confidence is slipping away."

Matt Fowler, co-founder of the COVID-19 Bereaved Families for Justice campaign group, said the PM had "already lost all credibility and the fact that the leader of the country is now under police investigation is deeply reprehensible".

Read more: What could Sue Gray's inquiry into No10 parties mean for PM and who decides what happens next?

How did we get here?

Disclosures surrounding a range of gatherings in Downing Street and a number of government departments during COVID restrictions in 2020 and 2021 have put pressure on Mr Johnson, with the PM facing calls to resign from opposition parties and some of his own backbench MPs.

In the latest revelation, Number 10 has admitted the PM had a birthday celebration inside Downing Street during the first COVID lockdown in 2020.

Mr Johnson has already admitted attending a garden party in Downing Street in May of that year, which was described by one of his aides as a "bring your own booze" event.

But he has claimed he thought it was a "work event" and that "nobody told me" it was against the rules.

The revelation that officials held two parties in Downing Street the day before the Queen sat alone at Prince Philip's funeral in April last year also provoked fury.

Number 10 later apologised to the Queen and said Mr Johnson was not in Downing Street that day.

What happens now?

The Met wrote to the Cabinet Office on Tuesday morning, formally requesting that it refers all relevant information from its inquiry in relation to the events under investigation to support the force's work.

Met Police Commissioner Dame Cressida Dick announced the force was investigating during an appearance in front of the London Assembly.

"As a result of the information provided by the Cabinet Office inquiry team and, secondly, my officers' own assessment, I can confirm that the Met is now investigating a number of events that took place at Downing Street and Whitehall in the last two years in relation to potential breaches of COVID-19 regulations," she said.

At this stage there is no estimate for how long its investigation will take, although sources have told Sky News it will take "weeks, not days".

Dame Cressida said the force will not be giving a "running commentary on our current investigations", but updates will be provided at "significant points".

And she said the fact that police were now investigating a number of events does not mean that fixed penalty notices "will necessarily be issued in every instance and to every person involved".

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Police had assessed "several other events" that appeared to have happened in Downing Street and in Whitehall, but they were not thought to have reached the threshold for criminal investigation, the commissioner told the London Assembly.

Former Met chief superintendent Dal Babu told Sky News the investigation will be "incredibly simple", suggesting it may not take long to finish.