Vatican City ? The Vatican was late to wade into the furor triggered by “The Da Vinci Code,” but now a top cardinal is crusading against the novel with the fervor of an exorcist.

Cardinal Tarcisio Bertone, a former Vatican official considered by some as possible pope material, is pushing a boycott of Dan Brown’s runaway best seller. The book, he insists, espouses heresy and deceives the world’s 1 billion Roman Catholics and others by distorting the origins of Christianity.

“There are certainly novels that offend millions of believers in their deepest faith, in their most lively hopes. I believe this is not acceptable,” Bertone said in an interview with Associated Press Television News.

Bertone, who worked in the Vatican’s powerful office on doctrinal orthodoxy before becoming Genoa archbishop, caused a stir this week by denouncing the book as proof of “anti-Catholic” prejudice and urging people not to buy it.

Allegations in the novel that Jesus Christ married Mary Magdalene and has descendants have outraged many Christians and have been dismissed by historians and theologians.

“The truth is that it spreads false ideas on the origins of Christianity to which we must answer with precise information and with a critical conscience,” Bertone said, clearly speaking for the Vatican. “We want to say the truth about this book. The truth will set them free. This is the word of the Lord.”

“The Da Vinci Code” — a fast-moving tale of code-breaking, art history, secret societies, religion and murder — was published two years ago and is available in 44 languages. Publisher Doubleday said there were 29 million copies in print but did not have global sales figures.

Booksellers expect the novel to remain a best seller well into this year. The book has spawned tours in Paris, London and Scotland, as well as a lineup of other books that purport to prove or debunk its claims. Director Ron Howard is making a Sony Pictures film based on the book starring Tom Hanks with a target release of May 2006.

Monsignor Javier Echevarria, who heads the conservative Catholic organization Opus Dei — highly admired by the pope but unflatteringly depicted in the novel — said Wednesday that Brown “knows he is doing wrong and he knows he’s deceiving the people.”

Doubleday defended it as a work of fiction whose ideas “have been circulating for centuries.”

“Doubleday certainly respects Cardinal Bertone, the Vatican and their desire to clarify any factual errors they feel may have been made in ‘The Da Vinci Code,'” it said.

In a statement on his Web site, Brown dismissed the furor, describing his novel as “an entertaining story that promotes spiritual discussion and debate.” Brown said he was often contacted by clergy who thank him for writing the book.

But Bertone, who hosted a seminar in Genoa this week titled “Story Without History” to rebut the novel’s depiction of Christ and the early church, insists it “should not present itself as a historically documented book.”

The Vatican “trusts that Christians have a mature conscience,” Bertone said. “But such a messy book can do damage.”