William Wragg’s sensational intervention heaped more pressure on Mr Johnson, dashing any hopes he may have of drawing a line under the episode. The Tory MP for Hazel Grove stopped short of calling for the Prime Minister to resign, saying it was a decision for Mr Johnson himself.

       Nevertheless, speaking after Prime Minister’s Questions, Mr Wragg did not mince his words.

       He told BBC Radio 4's PM it was "a tragedy things have come to pass in this way”.

       Referring to Mr Johnson’s statement in the House of Commons earlier on Wednesday, Mr Wragg said: "Unfortunately, I wasn't reassured.

       “I fear this is simply going to be a continuing distraction to the good governance of the country."

       He said it would be "preferable" for Mr Johnson to offer his resignation himself as MPs were "tired" and "frankly worn out of defending what is invariably indefensible".

       With Second Permanent Secretary in the Cabinet Office Sue Gary tasked with investigating the various allegations, Mr Wragg explained: "I don't believe it should be left to the findings of a civil servant to determine the future of the Prime Minister and indeed who governs this country.

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       “I think it is for the Conservative Party, if not the Prime Minister, in fact, to make that decision, and to realise what is in the best interest, so that we can move forward both as a party and a country."

       Mr Wragg said he had "no doubt the Prime Minister is reflecting deeply on what has happened, but I cannot in all sincerity see a way where these issues go away”.

       He added: "It is deeply unfortunate, but I'm afraid it is the inevitable conclusion is the only way to do that is with a change.”

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       The mood among Tory backbenchers remains sombre on Wednesday afternoon, with one telling Express.co.uk Mr Johnson was “safe for the time being”.

       Earlier, Mr Johnson said he attended the May 20, 2020, gathering for roughly 25 minutes to "thank groups of staff" but "with hindsight I should have sent everyone back inside".

       The Prime Minister acknowledged public anger, saying: "I know the rage they feel with me and with the Government I lead when they think in Downing Street itself the rules are not being properly followed by the people who make the rules."

       He said the inquiry was examining the situation but accepted "there were things we simply did not get right and I must take responsibility".

       Downing Street refused to say whether his then-fiancee, now-wife Carrie Symonds had attended the gathering, if Mr Johnson had noticed tables laden with food and drink or if he had brought a bottle of his own into the garden.

       The 1922 Committee represents Tory backbenchers sitting in the House of Commons.

       In order to force a leadership contest, a minimum of 15 percent of Tory MPs need to send letters of no-confidence to chairman Sir Graham Brady.

       There is so far no indication that such a threshold has been met.

       However, Tory MPs including Huw Merriman, Nigel Mills and Sir Roger Gale have all called for Mr Johnson to step down.

       Mr Gale, MP for North Thanet, said it was already clear that Mr Johnson had misled Parliament and was politically a "dead man walking".

       He added: “I think the time has come for either the Prime Minister to go with dignity as his choice, or for the 1922 Committee to intervene."