British Prime Minister Boris Johnson apologised to parliament on Tuesday 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 lawmakers secured a vote later this week into whether Johnson should be investigated over claims he misled parliament by repeatedly denying any breach, he said he now realised he was in the wrong.

Boris said that at the time 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,” Boris told parliament.

Opponents have called for Boris to resign, accusing him of misleading parliament after he told lawmakers 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 lawmakers to remove the Prime Minister to “bring decency, honesty and integrity back into our politics and stop the denigration of everything this country stands for”.

Pressure to resign from Boris’s own lawmakers has abated with the war in Ukraine in which he has sought to play a leading role in the West’s 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, used the occasion to tell Boris 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 Boris 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 Boris retains the support of most lawmakers in his Conservative Party and can still command a majority in parliament. But the debate will draw fresh attention to his conduct.

Boris 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 found his staff had enjoyed alcohol-fuelled parties.