The suit was started by British historians Richard Leigh and Michael Baigent who claim "the whole architecture" of their 1982 book "The Holy Blood and the Holy Grail" was copied by Brown and used without their approval. The two historians are also suing Random House, their publishing house, as it also published Brown's worldwide bestseller.

The "Da Vinci Code" sold 36 million copies worldwide and, like "The Holy Blood and the Holy Grail" (itself a bestseller) caused upset among Catholics because of the allegations that Jesus and Mary Magdalene were actually married and had a son.

The lawsuit might lead to a British ban on Brown's novel and on the Sony Pictures Hollywood adaptation for the big screen by director Ron Howard.

Part of the German media conglomerate Bertelsmann Random House dismissed the claims of the two authors as "without merit".

This is not the first trial Dan Brown and his famous religious thriller are involved in: last August, Brown won the lawsuit started by Lewis Perdue.

Perdue claimed that the "Da Vinci Code" had copied elements of two of his novels, "The Da Vinci Legacy" and
"Daughter of God".