(NBC) -- The Church of Scientology has alienated one of its most famous advocates.
Paul Haggis, the award-winning screenwriter of "Crash" and "Million Dollar Baby," spoke out against the church in an exclusive interview set to air on "Rock Center" Thursday night.
The 59-year-old filmmaker is the most prominent Hollywood figure ever to have left the church, which he now labels a cult.
"You've got these folks inside this fortress who won't look out and won't look at any criticism and can't bear any investigation and thinks that everyone is against them," Haggis told NBC's "Rock Center with Brian Williams." "How would you describe that? It's a cult."
In the interview, Haggis says his own research unearthed evidence of child abuse and involuntary confinement by church members. What he learned prompted him to abandon Scientology, he said.
Haggis admitted that Scientology helped him in the beginning, saying it's like "picking up any self-help book." But after more than 30 years in the church, he began questioning the religion and did not like what he discovered.
"I was ashamed of my own stupidity at how I could be so purposely blind for so many years," Haggis said.
"Rock Center" also talks to Lawrence Wright, who penned the new book about Scientology "Going Clear: Scientology, Hollywood and the Prison of Belief."
The Pulitzer Prize-winning author interviewed 200 people and pored over thousands of pages of documents for the book and said he also found evidence of young recruits working in unsafe conditions.
The Church of Scientology has denied those allegations and maintains that it adheres to all child labor laws.
"There is no record, no police reports, no medical records, no photos to support these allegations," the church said.
Rock Center's two-part report airs Thursday, Jan. 17, at 10 p.m., on NBC's "Rock Center with Brian Williams," on 11Alive.
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