UK Prime Minister Boris Johnson on Tuesday "categorically" denied claims by his former chief aide that he lied to parliament about a Downing Street party held during a strict lockdown.
But appearing in public for the first time after days of Covid self-isolation, Johnson also ducked questions about whether he would resign if an internal inquiry establishes that he did lie.
Johnson is battling damaging allegations that he and staff attended boozy events during Covid restrictions, prompting an investigation by senior civil servant Sue Gray.
The revelations have sparked public fury, leading to a double-digit lead in polls for the main opposition Labour party over Johnson's Conservatives, and calls from some Tories for him to quit.
Johnson has apologised for a May 20, 2020 party in the Downing Street garden, telling parliament last week he thought it was a "work event", despite an aide inviting staff to "bring your own booze".
But his combative former senior adviser Dominic Cummings, who has been waging a vendetta against Johnson since leaving Downing Street in late 2020, said he warned his then boss about the event at the time.
"I can tell you categorically that nobody told me, nobody said this was something that was against the rules, that it was a breach of the Covid rules, that it was something that wasn't a work event," Johnson said.
"Frankly I can't imagine why on earth it would have been allowed to go ahead," he told reporters on a visit to a London hospital.
Hanging his head in remorse, Johnson also renewed his office's apology to Queen Elizabeth II after it emerged that his staff held leaving parties during national mourning for her husband, Prince Philip, in April 2021.
Johnson's denials have been carefully worded, appearing to clear him of any personal blame even if there was wrongdoing by staff, and relying on a narrow exemption for work gatherings during lockdowns.
But in the latest of an incendiary series of blog posts, Cummings wrote that he told Johnson that Downing Street was becoming a boozy "madhouse". The prime minister "waved it aside", he added.
"The events of May 20 alone, never mind the string of other events, mean the PM lied to Parliament about parties," said Cummings, adding he was ready to swear to his account "on oath". (AFP)