Boris Johnson will face Prime Minister’s Questions in the midst of fresh allegations over what he knew about parties held at Downing Street during the coronavirus lockdown.
It comes as a growing number of Conservative MPs make their move to oust him from Number 10.
Under Conservative Party rules, a formal vote of no confidence can be triggered if 15% of the party’s MPs submit a letter to the backbench 1922 committee.
The committee, currently chaired by the backbench MP Sir Graham Brady, holds significant influence within the party.
Theresa May faced a vote of no confidence as prime minister in 2018 after the then-threshold of 48 letters was reached.
Despite winning the vote, May was out of Downing Street months later.
Based on the current number of MPs within the party, the threshold stands at 54 letters being required.
Johnson has insisted that he was not told that the gathering in Number 10 in May 2020 was against the rules.
“Nobody told me that what we were doing was against the rules, that the event in question was something that… was not a work event,” he said.
“And as I said in the House of Commons when I went out into that garden I thought that I was attending a work event.”
The Prime Minister said he carries “full responsibility” for what took place.
He continued: “I do humbly apologise to people for misjudgements that were made but that is the very, very best of my recollection about this event.
“That’s what I’ve said to the inquiry.
“I carry full responsibility for what took place but nobody told me. I’m absolutely categorical, nobody said to me this is an event that is against the rules.”