Film studio 20th Century Fox has rejected claims from a historian that they copied elements of one of his books for a forthcoming blockbuster.
Kingdom of Heaven stars Orlando Bloom and Liam Neeson
James Reston Jr has said the script for their epic Kingdom of Heaven is "strikingly similar" to a book he wrote about the Crusades.
However, the studio has said Reston's allegations are "wholly without merit".
Kingdom of Heaven, directed by Ridley Scott, is about a blacksmith who defends Jerusalem from the crusades.
Orlando Bloom, Liam Neeson and David Thewlis are among the co-stars.
Mr Reston alleges that Scott rejected an offer to direct a film based on his 2001 book Warriors of God: Richard the Lionheart and Saladin in the Third Crusade.
However, he claims that Scott then used his book as the basis for Kingdom of Heaven copying his main character, Bailin of Ibelin, as well as taking the film's title from a chapter heading.
Mr Reston's lawyer told the studio that his client would take legal action against the studio for copyright infringement unless he was given credit and compensation for the film.
However, Fox lawyer Bonnie Bogin said that he could not "claim a monopoly on history".
"The elements in Warriors of God are no more than historical facts which have been in the public domain for more than nine centuries," she said.
Kingdom of Heaven opens in the UK on 6 May.