British Prime Minister Boris Johnson has denied an accusation by his former adviser that he lied to parliament about a lockdown party, saying that nobody had warned him the “bring your own booze” gathering might contravene COVID-19 rules.

Mr Johnson faces the gravest crisis of his tenure after revelations about gatherings during COVID-19 lockdowns, some when British people could not even bid farewell in person to dying relatives and the Queen was mourning her husband.

Propelled into the top job to “get Brexit done”, Mr Johnson won his party’s biggest majority in more than 30 years but now faces calls to resign from opponents and even some of his own MPs.

Asked if he had lied to the public and parliament, Mr Johnson said: “No.”

“No. Nobody told me that what we were doing was, as you say, against the rules, that the event in question, was, something, we were going to do something that wasn’t a work event,” he said.

Mr Johnson sidestepped several questions about whether or not he would resign if it was proven that he had misled parliament.

Mr Johnson last week apologised to parliament for attending a “bring your own booze” gathering in the Downing Street garden on May 20, 2020.

He said he had thought it was a work event and that he attended for 25 minutes to thank staff.

But Dominic Cummings, an architect of Britain’s departure from the European Union and a former senior adviser who left the government under acrimonious terms in November 2020, said Mr Johnson had agreed the drinks party should go ahead.

Mr Cummings said that he and at least one other adviser told Principal Private Secretary Martin Reynolds, the official who invited people to the party, that it should not go ahead.

The warning was sent via email, according to Mr Cummings.

“I told the PPS the invite broke the rules,” he said.

“The idea that the PPS would be challenged by two of the most senior people in the building, say he’d check with the PM then not – is not credible.”

Mr Johnson’s apology came after ITV News published an email invitation from Mr Reynolds to the event.

Mr Cummings said that after being recommended to cancel the invitation, Mr Reynolds checked with Mr Johnson if it should go ahead.

“The PM agreed it should,” Mr Cummings said in his blog.

“The events of 20 May alone, never mind the string of other events, mean the PM lied to parliament about parties,” he wrote.

Senior civil servant Sue Gray is investigating about a dozen allegations of rule-breaking by Mr Johnson, his team and officials at 10 Downing Street.

Senior ministers have said people needed to wait for the conclusion of her inquiry.

-AAP