Prime Minister Boris Johnson apologized Wednesday for attending a garden party during Britain’s coronavirus lockdown in 2020, but brushed aside opposition demands that he resign for breaching the rules his own government had imposed.

Johnson is facing a tide of anger from public and politicians over claims he and his staff flouted pandemic restrictions by socializing when it was banned. Some members of his Conservative Party have joined in the criticism, saying he must quit if he can’t quell 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.