Donald Trump's All-Stars season pits returning contestants Gary Busey, Dennis Rodman, Lisa Rinna, La Toya Jackson, Stephen Baldwin and others against each other to crown the ultimate winner.
Filming on the NBC series took place while Omarosa was grieving for her late partner Michael Clarke Duncan last fall, but the reality star revealed Trump's special assistant Morgan showed no mercy in the boardroom.
"Donald [Trump] would try to back him off, but he was like a dog, like a hound dog on me and it was tough, because I was grieving and I wasn't bringing that into the boardroom, but it was there," Omarosa recalled to Access Hollywood.
She continued: "Everybody was kind of nurturing, everybody was very, very supportive, but he didn't care."
Omarosa went on to accuse Morgan of holding a grudge due to their clashes while previously competing against each other on The Celebrity Apprentice in 2008.
"[Piers was] singularly focused, tunnel focused on lobbying to get me off of the show, lobbying to get me fired," she claimed.
"It wasn't a mentor environment. It was the most toxic experience - I mean, to the point where my castmates went - on my behalf - to the powers that be, because it was so vile and so vicious and so personal."
Morgan's only reaction to Omarosa's comments thus far has been to call her "a nobody" on Twitter.
Omarosa gained her fame originally on the regular version of The Apprentice, in which she was fired in week nine.
The Celebrity Apprentice: All-Stars premieres on March 3 at 9/8c on NBC.