A letter warns of a defamation suit should the book, 'Ruthless: Scientology, My Son David Miscavige, and Me,' get a release in the U.K. next week as planned, while the publisher responds: "My plans for the book haven't changed at all."

Lawyers for David Miscavige are mounting an eleventh-hour attempt at preventing the publication of a new tell-all about the Church of Scientology leader. The author is Miscavige's own father, Ron Miscavige.

As first reported by Scientology observer Tony Ortega on his website, London-based publisher Silvertail Books has received a letter from Johnsons Solicitors, a powerful law firm "with a strong reputation for its expertise … in media and defamation," according to its website.

The letter warns of a defamation suit should the book, Ruthless: Scientology, My Son David Miscavige, and Me, get a May 3 release in the U.K. as planned. It goes on to say that St. Martin's Press, which is releasing the book in the U.S., has received a similar letter.

"As you are no doubt aware, U.K. and Irish libel laws offer more extensive protection to individuals, and indeed religious organizations, than those in the U.S.," the letter states. To a large extent that's true, as U.K. libel laws remain more plaintiff-friendly than in the U.S. However, in 2013, the U.K. amended its defamation laws to provide defenses of truth, opinion and — likely of relevance here — "publication on a matter of public interest."

Still, Miscavige's lawyers are hoping the laws will bend to their favor. "You are now on notice of the highly defamatory content of the subject book. 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," the letter continues, setting the stage for a father-son courtroom face-off.

Among the "malicious, false, misleading and highly defamatory" assertions made in the book: that Miscavige "seized power" from Scientology founder L. Ron Hubbard by "outmaneuvering rivals"; that "Gold Base" headquarters in Hemet, Calif., has "appalling conditions" and staff "were not permitted to leave"; that church members were "subjected to deprivation and violence" while detained in a prison-like containment center known as "the Hole"; and that Miscavige hired private detectives to trail his father.

Many if not all of these claims have been previously made in other Scientology exposés, including Lawrence Wright's Going Clear: Scientology, Hollywood and the Prison of Belief. The 2013 book was released throughout the U.S. and Europe, but, due to its libel laws, not in Britain; last month, Silvertail announced it would finally release the book there. (The accompanying Going Clear film aired in the U.K. on Sky Atlantic in September 2015 and was the most watched documentary on the channel in three years.)

Speaking from his London offices, Silvertail Books publisher Humfrey Hunter tells The Hollywood 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."

Ruthless will be the focus of a special this Friday on ABC's 20/20. The Church of Scientology did not respond to a request for comment.

The full letter is embedded below.