Catholic group wants 'Da Vinci' rating
They say children may not realise the "absurd" story is not true.
"Any adult can distinguish reality from fiction," explained spokesman Marc Carroggio. "But you cannot expect a child to make proper judgements."
"Merely adding a disclaimer that says 'fiction' is not enough," he continued. "It is well known that hateful images like this produce feelings of hatred in those who lack a critical sense."
However, Mr Carroggio said Opus Dei not make a "declaration of war" on the film, and adding that he though it could acts as "sort of indirect publicity for us."
He told Catholic agency Zenit: "No one is going to make threats or organise boycotts."
The Da Vinci Code, directed by Ron Howard and based on Dan Brown's best-selling book, is due for release in May.