The apology, which stopped short of admitting wrongdoing, was Johnson's attempt to assuage a tide of anger from the public and politicians over accusations he and his staff repeatedly flouted pandemic restrictions by socializing when it was banned.

The "partygate" scandal could become a tipping point for a leader who has weathered a series of other storms, with some members of Johnson's governing Conservative Party saying he must quit for breaking the rules.

Douglas Ross, the leader of the party's Scottish wing, said Johnson's "position is no longer tenable," and "I don't think he can continue as leader of the Conservatives."

Trying to calm the furor, Johnson acknowledged for the first time Wednesday that he went to a May 2020 garden party at his Downing Street office, though he said that he had considered it a work event to thank staff for their efforts during the pandemic.