Boris Johnson is battling to stay in office, amid a growing wave of resignations from his government in protest at his leadership.
New chancellor Nadhim Zahawi has urged unity after his predecessor, the health secretary, and several junior ministers walked out.
But the prime minister has been hit by five further resignations, taking the total to 15 in the past day.
It comes as he prepares for PMQs later and a grilling by senior MPs.
Mr Johnson's premiership has been plunged into crisis following the dramatic resignations of Chancellor Rishi Sunak and Health Secretary Sajid Javid.
They quit within minutes of each other on Tuesday following a row over Mr Johnson's decision to appoint Chris Pincher deputy chief whip earlier this year.
Five further resignations have followed on Wednesday, including education ministers Will Quince and Robin Walker, Treasury minister John Glen, and ministerial aides Laura Trott and Felicity Buchan.
Mr Javid, who has now resigned from Mr Johnson's cabinet for the second time, will make a resignation statement to Parliament later.