A top Scientologist is threatening to use Northern Ireland's stricter libel laws to prevent a book written by his father from being published.
The tell-all account by the father of David Miscavige, leader of the church of Scientology, is due to be released in the UK and Ireland this week.
Ruthless: Scientology, My Son David Miscavige and Me, written by Ron Miscavige, is to be published on both sides of the Atlantic on Tuesday.
The book is believed to allege that David Miscavige seized power from L Ron Hubbard, the founder and former leader of Scientology, and makes claims about how members of the church are treated.
David Miscavige denies all of his father's allegations.
Belfast-based law firm Johnsons sent a legal letter on behalf of David Miscavige to the UK-based Silvertail Books, which plans to release Ruthless on Tuesday.
The letter said the church objected to the "false and defamatory allegations contained within" the book, and if publication goes ahead "our client will be left with no alternative but to seek the protection of UK/Irish defamation and other laws".
The Sunday Times has reported that the letter also said the church's US representatives had written to St Martin's Press, which is publishing the book in America outlining the "sinister background" of Ron Miscavige.
Humfrey Hunter, the founder of Silvertail, released a statement to the Sunday Times.
"All the legal due diligence has been done so it is published responsibly, but I wasn't surprised to get the letter because they will try anything they can to fight their corner," he said.
Mr Hunter said the legal threat would not affect plans for the release, and he was confident at being able to defend a legal challenge.
"(Ruthless) shines a light on the person at the head of the church - it's a story that's never been told," he said.
"The Church of Scientology has only ever had two leaders: L Ron Hubbard and then David Miscavige.
"Miscavige is a hugely significant figure in the church. People have written things about him, but no one has ever written from a perspective as close as this. It's utterly fascinating."
The law on defamation was updated in England and Wales in 2013. Under the new guidelines, claimants have to show they have suffered "serious harm" before suing.
However, the reforms do not apply in Northern Ireland after being blocked by Stormont.
It has prompted warnings that our unreformed system poses a threat to freedom of speech.
Last April a hard-hitting Scientology documentary was axed from UK TV screens because of Northern Ireland's libel laws.
Controversial HBO expose Going Clear made allegations of abusive practices at the religion's US headquarters.
It was due to air in the UK in April 2015 to coincide with its American release.
But the programme was pulled by Sky because of fears it could face legal action under our stricter legislation.