A New Zealand author is embroiled in a plagiarism row over Dan Brown's blockbuster hit, the religious thriller The Da Vinci Code, and has launched legal action against the novel's publishers.
Nelson-born Michael Baigent and American writing partner Richard Leigh are suing Random House Group in Britain, claiming damages that could run to millions of dollars.
The Da Vinci Code joined the New York Times bestseller list at No 1 and has sold more than 12 million copies internationally.
Before the lucrative Christmas sales week it had sold about 100,000 here and remains at No 1 on the local bestseller list.
It has reportedly earned Brown £140 million ($380 million) and is about to be turned into a Hollywood movie starring Tom Hanks.
But Baigent and Leigh, whose own 1982 work Holy Blood, Holy Grail caused such religious outrage when it was published that it sparked death threats, say Brown has lifted large tracts of their research without permission.
Their lawsuit claims at least £150,000 damages for breach of copyright, saying a "substantial" amount of their work has been used and asking that copies of The Da Vinci Code be destroyed.
Baigent told the Weekend Herald the United Kingdom lawsuit meant he could not talk about the case, or which parts of The Da Vinci Code he and Leigh say amount to plagiarism.
"All I can tell you is that we are suing Dan Brown for theft of intellectual property.
"The matter's with the High Court, it's sub judice, and I can't say anything more than that unfortunately.
"It's never a nice thing for one writer to have to be suing another."
Random House spokeswoman Clare Harrington said from London that the publishers would file their defence with the court soon.
"We continue to be confident that the claimants' case is wholly without merit," she said.
Details of the allegations made by Baigent and Leigh remain sealed by the British court.
However there are clear links between Holy Blood, Holy Grail and The Da Vinci Code, even though the latter is a novel and the former a non-fiction study of secret religious history.
It also appears the identities of Baigent and his two co-authors have provided Brown with material for his characters.
Sir Leigh Teabing is a central character in The Da Vinci Code, but that name combines Richard Leigh's surname and an anagram of Baigent, and Sir Leigh's physical description is said to be similar to The Holy Blood's third co-author, Henry Lincoln.
Brown's hero is American professor of religious symbology Robert Langdon. Baigent has completed a masters degree that included a dissertation on Renaissance symbolism.
Holy Blood, Holy Grail has also sold millions of copies, and aroused controversy through its exploration of a theory that Jesus might not have died on the cross but lived, married and had children.
Their research explored whether a secret bloodline existed, and potentially challenged central foundations of Christianity - including the role of women.
It featured societies such as the Knights Templar and Priory of Sion, which are also core to mysteries within The Da Vinci Code.
Anger at Holy Blood, Holy Grail prompted death and bomb threats against the authors and publishers, and Baigent still keeps his address in England a secret.
He was reluctant to outline why he was taking legal action, but has told the Daily Telegraph newspaper in Britain that being "lumped in" with Brown's novel degraded the historical implications of their research.
"It makes our work far easier to dismiss as a farrago of nonsense.
"What a lot of people have forgotten was that the Holy Blood was a hypothesis," Baigent told the Weekend Herald this week.
"We had a lot of data that we were deeply suspicious of, and we spent a lot of time checking it.
"We managed to establish that a certain amount was shown to be correct; the rest was plausible."
Baigent, 56, has lived in the UK since 1976 but still visits home and family here most years.
Holy Blood, Holy Grail: Non-fiction study of secret religious history. Explores theory that Jesus might not have died on the cross but lived, married and had children.
The Da Vinci Code: Fiction. A novel about secret religious societies, cover-ups and explorations of persistent riddles - from the Mona Lisa's smile to the mystery of the Holy Grail.