Scientology honcho Miscavige threatens to sue own father to block book that could finally bring down ‘church’

High-ranking Church of Scientology member David Miscavige's lawyers have threatened to file suit against Miscavige's father Ron. The threat is a last-ditch effort to stop Ron Miscavige from releasing a tell-all book about his son's involvement in the religion, a belief system that outsiders and former members call a cult.

The Hollywood Reporter said Tuesday, "As first reported by Scientology observer Tony Ortega on his website, London-based publisher Silvertail Books has received a letter from Johnsons Solicitors," a law firm that specializes in high-profile defamation cases.

Ron Miscavige's book -- titled Ruthless: Scientology, My Son David Miscavige, and Me -- is set for release in early May. Silvertail reported that the book's U.S. publisher, St. Martin's Press, received a similar letter from attorneys representing David Miscavige. The letters threatens to file defamation suits should the book go to print in its current form.

"You are now on notice of the highly defamatory content of the subject book," the letter warned. "Accordingly, in the event that you proceed with the release of this book, in total disregard for the truth, our client will be left with no alternative but to seek the protection of UK/Irish defamation and other laws."

Silvertail Books publisher Humfrey Hunter told the Reporter, "My plans for the book haven’t changed at all since I received the letter. Full legal due diligence has been carried out on the manuscript and I am both confident in its integrity and very proud that Silvertail is publishing it. Ron’s story is an important one, and he is a brave man to be telling it."

Miscavige has been the head of the Scientology Church since the retirement of founder L. Ron Hubbard. His close friendship with actor Tom Cruise has been the subject of media speculation, which has also centered around the disappearance of his wife Shelly, who has not been seen or heard from in more than a decade.

ABC's 20/20 will feature Ruthless in this week's broadcast, which is set to air on Friday.