Nadine Dorries has said she would quit if she was Dominic Raab, as the deputy PM battles an "avalanche" of bullying allegations.
Pressure is mounting on Rishi Sunak to suspend him, as claims emerged that the cabinet secretary was aware of accusations before Mr Raab was brought back into the cabinet.
Meanwhile anti-Brexit campaigner Gina Miller claimed the top Tory had made her feel "bullied and demeaned" in an encounter at the BBC.
Mr Raab has denied any wrongdoing as an independent lawyer investigates eight formal complaints believed to involve dozens of civil servants.
Last night his former cabinet colleague said she didn't think it would be long before he quit.
Ms Dorries told TalkTV that while her dealings with Mr Raab had been "positive", she thinks he will get to the position where he decides to quit "pretty soon".
She said:: "If I were Dominic Raab and I was under this avalanche of accusations being made against me I think I would want to stand down, I would want to dedicate my time to clearing my name and refuting those allegations.
"And I think Dominic's probably going to get to that position pretty soon."
The Prime Minister is under pressure to reveal how much he knew about allegations about Mr Raab's conduct.
The Times reports that cabinet secretary Simon Case was informed of a written complaint about him months before he was reappointed by Mr Sunak last year.
He was reportedly told that the allegations were being "taken seriously".
And anti-Brexit activist Ms Miller has accused Mr Raab of an "abusive attack" in the build-up to the 2016 referrendum.
Writing in The Independent she claimed she saw him shouting "get me a f***** car" at a "shaking" young man outside the studio.
She said: "Raab was aggressive and intimidating, and I was bullied and demeaned.
"This was an aggressive male expressing seemingly misogynistic behaviour."
Earlier this week The Mirror reported witnesses also claim the Deputy PM would switch his anger on and off depending on whether it was civil servants or ministers in the room.
Mr Raab's spokesman has previously said he “looks forward to answering the allegations made of him directly”.
Mr Raab insisted last week: “I’m confident I behaved professionally, and of course the Government takes a zero-tolerance approach to bullying.”
Mr Sunak has tasked lawyer Adam Tolley KC with investigating bullying claims against Mr Raab, with dozens of civil servants believed to be involved in eight formal complaints.
