British Prime Minister Boris Johnson has apologised to parliament after he was fined by police for breaking lockdown rules, saying he did not know a birthday gathering at the height of the pandemic was in breach of the rules he had set.

On the same day that opposition MPs secured a vote later this week into whether Mr Johnson should be investigated over claims he misled parliament by repeatedly denying any breach, he said on Tuesday he now realised he was in the wrong.

Mr Johnson said that at the time – June 2020 – it had not occurred to him he was in breach of the rules.

He said the public had the right to expect higher standards.

“As soon as I received the notice, I acknowledged the hurt and the anger, and I said that people had a right to expect better of their Prime Minister,” Mr Johnson told parliament.

Opponents have called for Mr Johnson to resign, accusing him of misleading parliament after he told MPs last year that all rules were followed in Downing Street – the prime minister’s official residence and workplace – during the pandemic.

Labour leader Keir Starmer urged MPs to remove Mr Johnson to “bring decency, honesty and integrity back into our politics and stop the denigration of everything this country stands for”.

Pressure to resign from Mr Johnson’s own MPs has abated with the war in Ukraine, in which he has sought to play a leading role in the international response.

While a handful have repeated calls for him to go, most say now is not the time.

However, Mark Harper, a former Conservative chief whip who once helped maintain party discipline, used the occasion to tell Mr Johnson in the chamber that he needed to quit, saying he did not believe “he is worthy of the great office that he holds”.

Lindsay Hoyle, the House of Commons Speaker, granted opposition parties’ request for a vote on Thursday on whether Mr Johnson should be referred to the privileges committee for an inquiry.

Under the ministerial code, knowingly misleading parliament is an offence that should result in resignation.

However, the motion is unlikely to pass because Mr Johnson retains the support of most MPs in his Conservative Party and can still command a majority in parliament.

But the debate will draw fresh attention to his conduct.

Mr Johnson insisted in December that “all guidance was followed completely” over the lockdown restrictions.

He was fined by the police last week after a damning internal inquiry concluded his staff had enjoyed alcohol-fuelled parties when people from different households were not allowed to meet indoors.

In his first statement to parliament since being handed the fine, Mr Johnson attempted to deflect some of the criticism by talking about other issues he is dealing with, including the war in Ukraine, the energy crisis and immigration.

The pressure is likely to build on the Prime Minister, however, with other Conservative MPs expected to take the party’s performance in local elections on May 5 and voter perceptions of Mr Johnson into account.

A poll by JL Partners for The Times newspaper, which asked almost 2000 people to give their view of the PM in a few words, found comments from 72 per cent of respondents were negative compared to 16 per cent that were positive.

The most common word used was “liar”, it reported.

John Whittingdale, a former Conservative minister, said that while many of his constituents are angry, now was not the time to replace the Prime Minister because of the war in Ukraine.

“We currently face the gravest crisis in our global security for a long time and it is essential that we remain focused on beating [Russian President Vladimir] Putin and stopping the aggression against Ukraine,” he said.