The King of Queens actress, who also penned a book about the controversial religion after she left, told ABC News that Ron Miscavige "has a right to tell his story."
Ruthless: Scientology, My Son David Miscavige, and Me, Ron's book, details what Ron believes is David's "brutal approach to running the organization." In an interview with ABC's 20/20 ahead of the book's May 3 release, Ron said that his estranged son, now 55, "really decided at a very young age to make [Scientology] his career and his mission."
After Remini heard that Ron – who joined the church in the late 1960s – had left Scientology, she said she "tracked him down."
"I called him and I offered my support because I know he must have felt alone," she told ABC, referencing her own bumpy exit from the church. "I just wanted him to know that we were willing to take them in. There is no place for them to go unless they have family outside of the church, which is very rare."
She added that she "immediately" encouraged him to write a book. "We're all gonna speak up. You're not gonna just bully people telling their stories."
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The church has slammed Ron over Ruthless, with Monique Yingling, an attorney representing Scientology, telling ABC that the memoir is a "literary forgery."
"There seems to be no explanation except that his father is trying to make a buck off his name," she said. "So I think there's that level of sadness and I'm sure a sense of betrayal."
Other attorneys working on behalf of David contacted the book's U.K. publisher as well, threatening to sue if Ruthless is published.
The letter reportedly indicated that the U.S. publisher, St. Martin's Press, received a similar threat.
Remini has been in conflict with the church since her departure, with Scientology officials previously writing in a statement of her claims against David, "It comes as no surprise that someone as self-absorbed as Leah Remini with an insatiable craving for attention would exploit her former faith as a publicity stunt. "
ABC's full interview with Ron will air on 20/20 on Friday at 10 a.m. EST.