Leah Remini is set to make millions from her Scientology tell-all book.

A publishing ex ecutive told RadarOnline: “Everybody wants the Remini book. If she’ll tell all about her years in Scientology, her interactions with other celebrities in the religion, and what she went through in getting out - well, the sky’s the limit.

“If she were to lift the lid off how the church really operates under David Miscavige and how Tom Cruise fits in, that would up the ante.

“It would have to be a thought-provoking, sometimes funny, sometimes scary, sometimes sad look at Hollywood and Scientology that reveals information never previously known to the public.

“Leah comes across as very bright, articulate and sassy. She definitely has it in her to write a best-seller.”

The 43-year-old actress recently vowed not to "shut up" about the secretive sci-fi cult.

She said: "We stand united, my family and I, and I think that says a lot about who we are, and what we're about.

"I believe that people should be able to question things. I believe that people should value family, and value friendships, and hold those things sacrosanct.

"That for me, that's what I'm about. It wouldn't matter what it was, simply because no one is going to tell me how I need to think, no one is going to tell me who I can, and cannot, talk to.

"It doesn't matter, it could be anything. I thought about the family being broken up for some other cause, and I'm not about to shut up."