"He is an abusive person. I witnessed it, I’ve been a recipient of it on a small level," Remini wrote. "This is the real Tom."
The outspoken Scientology critic said Newton had "huge balls" following her candour about working with Cruise on Mission: Impossible 2'.
The "That's '70s Show" actor was charged in Los Angeles with forcibly raping three women in the early 2000s.
He could face 45 years to life in state prison if found guilty.
The two high-profile Scientologists have been linked together in the tabloids for years.
The “Second Act” star talks her enduring friendship with Jennifer Lopez and a future that leaves Scientology behind.
On Pinkett Smith’s Facebook show, “Red Table Talk,” the actresses gave their versions of the events that led up to their falling out.
“It’s time for us to tell our story,” the organisation said.
In a recorded phone call obtained by HuffPost, Jenni Weinman, the longtime publicist of actor Danny Masterson, suggested
"I have studied Dianetics, and appreciate the merits of Study Tech… but I am not a Scientologist."