Boris Johnson has offered a “full apology” and confirmed he has paid a fixed penalty fine for attending a birthday party in Downing Street in June 2020, but insisted that it “did not occur to me” at the time that he had broken the rules.

       Defending himself against accusations that he misled parliament over parties at No 10, Mr Johnson insisted that he “spoke in completely good faith” when he told the House of Commons that no Covid rules were broken.

       And he made clear that he will not resign after becoming the first sitting UK prime minister ever to be found by police to have broken the law.

       Asked if he will quit, he replied: “I want to be able to get on and deliver the mandate that I have.”

       Speaking at his countryside retreat Chequers shortly after it was revealed that he was among a total of more than 50 ministers, advisers and officials to receive fixed penalty notices, Mr Johnson made clear that he recognised he could face further fines as the Metropolitan Police’s Operation Hillman inquiry continues.

       Recommended Boris Johnson pays Covid fine and apologises for lockdown breach Carrie Johnson pays fine and apologises over PM’s birthday party in Cabinet Room What we know about the birthday party linked to Boris Johnson’s fine

       Notices were issued to the PM, his wife Carrie and chancellor of the Exchequer Rishi Sunak in relation to a surprise birthday party held for Mr Johnson in the Cabinet Room at No 10 on 19 June 2020.

       But Mr Johnson is also known to have attended three or more of the other 11 events being investigated by Scotland Yard.

       Confirming that he had been fined over the birthday party - at which a close ally previously said he was “ambushed with a cake” - Mr Johnson said: “I’ve paid the fine and I once again offer a full apology and in the spirit of openness and humility I want to be completely clear about what happened on that date.”

       He said that he had started work at 7am that day, chaired eight meetings and gone on a visit to Hemel Hempstead before on his return to Downing Street “there was a brief gathering in the Cabinet Room shortly after 2pm lasting for less than 10 minutes, during which people I work with kindly passed on their good wishes”.

       And he added: “I have to say in all frankness at that time it did not occur to me that this might have been a breach of the rules.”

       Mr Johnson said he “fully respects” the outcome of the Metropolitan Police investigation and that he accepts that voters “had the right to expect better” from him.

       “I understand the anger that many will feel that I myself fell short when it came to observing the very rules which the government I lead had introduced to protect the public,” said Mr Johnson.

       “And I accept in all sincerity that people have the right to expect better. Now I feel an even greater sense of obligation to deliver on the priorities of the British people - strengthening our economy, creating jobs and opportunities, levelling up across the whole of the United Kingdom, and now of course ensuring that Putin fails in Ukraine and easing the burden on hardworking families caused by higher energy prices.

       “I take that task with due humility but with maximum determination to fulfill my duty and do what’s best for the country I serve.”

       But he brushed off calls from opposition leaders and bereaved families for him to resign, saying: “I believe it’s my job to get on and deliver for the people of this country. That’s what I’m going to do.”

       Recommended MPs seek Parliament recall as PM and Chancellor fined over lockdown breaches Those who say time is not right for leadership change ‘couldn’t be more wrong’ Carrie Johnson to be fined for breaking Covid lockdown rules

       Challenged over the numerous parties alleged to have been held in Downing Street, which is his workplace as well as his home, he said: “Of course I take full responsibility for everything, but don’t forget the Downing Street is about, you know, 15,000 square feet. It’s got a lot of officials working in it – hundreds and hundreds of officials. I couldn’t be everywhere at once.

       “But clearly once it became obvious what had been happening, the types of behaviour that unfortunately sadly we’d seen, we’ve taken steps to change things and Downing Street has been radically transformed.”