There are reports that up to 20 Tory MPs are planning to submit letters calling for a change in leadership today.
54 are needed to trigger a vote.
It's over claims the Prime Minister knew that a Downing Street garden gathering during lockdown in 2020 was against the rules - something he 'categorically' denies.
He's facing more questions about his future as an inquiry gets underway.
Johnson said "we will have to see what she [Sue Grey] says.
"I think she should be given the space to get on with and conclude her inquiry, and I would urge anybody who has knowledge of this to tell her what they know."
