An exposé about internal Scientology leadership struggles between founder L. Ron Hubbard and current leader David Miscavige is at the center of a controversy. The book alleged poor living conditions and violence at the organization’s headquarters in California.

The book, entitled ‘Ruthless: Scientology, My Son David Miscavige, and Me’, was written by Ron Miscavige. Among the allegations in the book is that David “seized power” from Scientology founder L. Ron Hubbard.

Scientology leader David Miscavige threatens to sue over father's tell-all https://t.co/bBcIxYcInlpic.twitter.com/AvWKrs4mu6 — Hollywood Reporter (@THR) April 26, 2016

Elsewhere in the purported disclosure, the author accuses his son of of “outmaneuvering rivals,” keeping “appalling conditions” at the headquarters in Hemet, California as well as detailing how church members are subjected to “deprivation and violence” while detained in a prison-like confinement center known as “the Hole,” according to the Hollywood Reporter.

David Miscavige’s father also alleges that his son hired a private detective to trail him. The book is due for release in the UK on May 3.

The Church of Scientology is a body of beliefs and practices created by American science fiction author L. Ron Hubbard, which now characterizes itself as a religion. However, the movement began as an alternative to psychiatry known as Dianetics, which is widely perceived as pseudoscientific. The practice argues that personality flaws and ailments were the result of repressed negative memories and could be resolved through a counseling technique called auditing.

Scientology is absurd. But it doesn't claim woman was made from a rib.

'Scientology leader's dad writes tell-all' https://t.co/lPIfS1REsZ — Pitt Griffin (@pittgriffin) April 26, 2016

Scientology claims to give the believer a complete and total understanding of “one’s true spiritual nature,” however, in order to access the highest levels of the church, staggering payments are required. Many of the Church’s key figures are notably rich and famous, including Tom Cruise. Members of the Church are skeptical of modern medicine and believe in cleansing one’s own spirit.

The Church of Scientology has encountered considerable opposition and controversy and has been classified as a cult by some public authorities.

Ron Miscavige’s UK publisher, Silvertail Books, has already received a letter from a law firm warning of a defamation lawsuit if the book is released, according to Tony Ortega, who is a Scientology observer.

“As you are no doubt aware, UK and Irish libel laws offer more extensive protection to individuals, and indeed religious organizations, than those in the US,” the letter from Johnsons Solicitors states. “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.”

Miscavige’s lawyers are hoping the law will favor them. St. Martin’s Press is due to release the book in the US and has received a similar letter.

Many of the claims in the book have been alleged before in other Scientology exposés such as Lawrence Wright’s Going Clear: Scientology, Hollywood and the Prison of Belief in 2013. The book was released in the US and Europe but not in the UK because of its libel laws.

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