LONDON: UK Prime Minister Boris Johnson was fighting for his political future on Thursday, as his Conservatives descended into open internal warfare after he was forced to apologise for attending a boozy lockdown party.

The apparent breach of coronavirus restrictions has enraged the public, who were forced to abide by the rules and prevented them from visiting sick and dying loved ones, or attending funerals.

Most cabinet members rallied round Johnson after his mea culpa, but the backing given by some such as Rishi Sunak, his powerful finance minister and potential successor, was distinctly lukewarm. The prime minister himself went to ground on Thursday, cancelling a planned trip to northern England after a family member came down with Covid-19, in scrupulous adherence to his government’s rules.

While expressing “heartfelt apologies”, Johnson on Wednesday sparked ridicule by saying he had believed the May 2020 gathering was a work event. He urged all sides to await the findings of an internal inquiry.

Douglas Ross, the Conservatives’ leader in Scotland, joined at least four Tory backbench MPs in calling for Johnson to quit after the prime minister admitted joining the party in his Downing Street garden in May 2020, when Britain was under a strict lockdown.

“Regretfully, I have to say his position is no longer tenable,” Ross told STV. Cabinet member Jacob Rees-Mogg dismissed Ross as a “lightweight figure” in the ruling party, sparking rebukes from other MPs and warnings that the upper-crust Englishman was bolstering the case for Scottish independence.

Northern Ireland Secretary Brandon Lewis insisted Johnson had been “very, very sincere” in his apology, amid warnings that Conservative MPs could be mobilising for a no-confidence vote.

“He does recognise the anger and upset and frustration that people feel at what they perceive happened at Number 10. He recognises that and takes responsibility,” Lewis told BBC radio.