Boris Johnson has claimed his partygate fine “did not breach” the Ministerial Code as there was “no intent to break the law”.

The Prime Minister, whose Government brought in the coronavirus regulations, was issued a fixed penalty notice (FPN) over a birthday party thrown in his honour in the Cabinet Room in June 2020 at a time when indoor socialising was banned.

But Mr Johnson, in a letter to his independent adviser on the Ministerial Code, said his judgment on why he did not break the rules for ministers included that there have been “past precedents of ministers who have unwittingly breached regulations where there was no intent to break the law”.

His remarks came in response to the latest annual report from Lord Geidt, who said a “legitimate question” had arisen as to whether the case of the FPN might have constituted a breach of the “overarching duty within the Ministerial Code of complying with the law”.

Mr Johnson, in a letter released on Tuesday evening, said he had taken “full responsibility for everything that took place on my watch” in light of lockdown-busting gatherings in Downing Street and pointed to his House of Commons apology.

He reiterated there was “no intent to break the regulations”, adding: “I did not consider that the circumstances in which I received a fixed penalty notice were contrary to the regulations.

“I have accepted the outcome and paid it in compliance with legal requirements. Paying a fixed penalty notice is not a criminal conviction.”

He added: “In relation to the fixed penalty notice for my attendance in the Cabinet Room on June 19 2020, I believe that, taking account of all the circumstances, I did not breach the code.

“In coming to that conclusion, (a) I have duly considered past precedents of ministers who have unwittingly breached regulations where there was no intent to break the law; (b) I have been fully accountable to Parliament and the British people and rightly apologised for the mistake; (c) I have corrected the parliamentary record in relation to past statements; and (d) I have followed the principles of leadership and accountability in doing so.

“In my view, the same principles apply to the fixed penalty notice paid by the Chancellor of the Exchequer.”

Mr Johnson was last week accused of watering down the code after the Government said it was being updated – making clear that ministers will not necessarily have to resign for more minor violations.

Instead the Prime Minister will have the option of imposing a lesser sanction such as “some form of public apology, remedial action or removal of ministerial salary for a period”.

Mr Johnson was also criticised for refusing to give Lord Geidt the freedom to launch his own inquiries into possible breaches and he would still need the Prime Minister’s consent before proceeding.

Lord Geidt, in the preface of his annual report, said: “Granting the independent adviser an independent right to initiate inquiries into ministerial conduct has been called for over many years.

“The changes now offered by the Government are at a low level of ambition.

“Nevertheless, given the new provision for greater transparency in the event of a Prime Minister intervening to prevent an independently initiated inquiry from proceeding, I believe that under normal circumstances this would be a workable scheme.

“The grounds for refusal by a Prime Minister would need to pass a very high standard, such as national security. Even then, an independent adviser would now generally be able publish the reasons for a Prime Minister’s refusal.”