Boris Johnson has refused to rule out the possibility that he may resign after taking “full responsibility” as he apologised for attending a party in the Downing Street party.

The Prime Minister made his first public appearance since the leak on Monday of an email from his principal private secretary, Martin Reynolds, inviting Downing Street staff to the gathering in May 2020 to “make the most of the lovely weather”.

The disclosure triggered a new wave of public anger following the reports last year of parties in the run up to Christmas 2020, with Tory MPs openly warning Mr Johnson his position will be untenable if he has been shown to have lied.

Boris Johnson apologises over Downing Street party

Mr Johnson apologised to MPs and the country for allowing parties to go ahead in the Number 10 Downing Street garden.

Boris Johnson told the Commons: “With hindsight I should have sent everyone back inside. I should have found some other way to thank them.

“I should have recognised that even if it could be said technically to fall within the guidance, there are millions and millions of people who simply would not see it that way, people who have suffered terribly, people who were forbidden for meeting loved ones at all inside or outside, and to them and to this House I offer my heartfelt apologies.

“All I ask is that Sue Gray be allowed to complete her inquiry into that day and several others so that the full facts can be established.”

The PM suggested he did not realise he was at a party at the time.

Mr Johnson told the Commons: “No 10 is a big department with a garden as an extension of the office which has been in constant use because of the role of fresh air in stopping the virus.

“When I went into that garden just after six on May 20, 2020, to thank groups of staff before going back into my office 25 minutes later to continue working, I believed implicitly that this was a work event.”

Boris Johnson refuses to rule out resignation as Prime Minister

Labour leader Sir Keir Starmer asked if Boris Johnson would resign after labelling it “ridiculous” that the Prime Minister suggested he “didn’t realise he was at a party”.

After being asked specifically whether he would resign, rather than saying no, the Prime Minister said he will not “pre-empt the outcome of the inquiry” into the parties at Downing Street.