Boris Johnson insisted that he believed a party held in lockdown by Downing Street staff was a work event as he declined to confirm whether he would resign if it emerged he had misled parliament.
Speaking to reporters on Tuesday morning, the prime minister denied he had been told of the gathering ahead of time.
It contradicts claims from his former adviser Dominic Cummings that he had been warned about the event in advance - but refused to take action.
“I’ve seen the email from Martin Reynolds. Clearly that was not phrased in a way that was right,” he told Sky News. “I only saw it when it emerged (in the press”.
Asked if he would resign if the report concluded he had misled MPs, he said: “We’ll have to see what Sue Gray says. She could be given the space to get on with her inquiry.”
The ministerial code states: “Ministers who knowingly mislead Parliament will be expected to offer their resignation to the Prime Minister.”
Earlier on Tueday, Chancellor Rishi Sunak insisted he “believes” the prime minister’s explanation.
Asked whether Mr Johnson would have to resign if it was proven he had lied to parliament, Sunak said: "I’m not going to get into hypotheticals. The ministerial code is clear on these matters.
"But as you know, Sue Gray is conducting an inquiry into the situation. I think it’s right that we allow her to conclude that job."
The Chancellor was not present at prime minister’s questions last Wednesday while Mr Johnson made his apology to MPs, fuelling speculation in Westminster that he was attempting to distance himself from the crisis.
