Hundreds of churches are preparing events to coincide with the release next month of the film version of the novel, to help congregations understand why the version of events that appears in the book is untrue. The Da Vinci Code is based on the premise that Jesus married Mary Magdalene and had a child, leading to a secret bloodline that was suppressed by the Roman Catholic Church and was the Holy Grail of legend.

In his Easter Day sermon at Canterbury Cathedral Dr Williams said that the discovery of the Coptic text of a "Gospel of Judas" and the publication of The Da Vinci Code might appeal to a sense of mystery but did not match the challenges posed by the Resurrection.

It had become customary, he said, to mark Christian festivals with "a little flurry of newspaper articles and television programmes raking over the coals of controversies about the historical basis of faith". He added that the Church's position within the Establishment meant that it was mistrusted.

Modern society was fascinated by conspiracies and cover-ups, he said. Biblical texts were treated "as if they were unconvincing press releases from some official source, whose intention is to conceal the real story; and that real story waits for the intrepid investigator to share it with the waiting world.

"Anything that looks like the official version is automatically suspect. Someone is trying to stop you finding out what really happened, because what really happened could upset or challenge the power of officialdom. It evokes Watergate and All the President's Men.

The truth, Dr Williams said, was more prosaic. "The Bible is not the authorised code of a society managed by priests and preachers for their private purposes but the set of human words through which the call of God is still uniquely immediate to human beings today, human words with divine energy behind them."

People have become used to asking cynical questions, Dr Williams said. "We have become so suspicious of the power of words . . . the first assumption we make is that we're faced with spin of some kind. The modern response to the proclamation 'Christ is Risen!' is likely to be, 'Ah, but you would say that, wouldn't you? Now what's the real agenda?' "

Yet the New Testament "was written by people who by writing what they did made themselves less powerful, not more. They were walking out into an unmapped territory, away from the safe places of political and religious influence . . . it was written by people who were still trying to find a language that would catch up with a reality bigger than they had expected. Whatever this is, it is not about cover-ups, not about the secret agenda of power."

Dr Williams, an expert on early heresies, said that the "Gospel of Judas" was a late text from a community on the fringes of the early Church.

He said that the world's praying and suffering Christians were the real testament to the truth of the Resurrection. "If we want to know what it is about today, we need to turn to the people who are taking the same risks, struggling with the same mystery. We need to look at the martyrs and the mystics. There are places where conversion to Christianity is literally a matter of putting your life on the line. We have all been following the story of Abdul Rahman in Afghanistan, and his story is not unique. Whatever the Gospel means in circumstances like that, it isn't a cover-up for the sake of the powerful."

Dr Wright, an evangelical theologian, says that Brown's novel "corresponds to what a great many people want to believe and to do, rather than to the hard and bracing challenge of the very Jewish gospel of Jesus." It "appears to legitimate a free-for-all, do-it-yourself spirituality". The bishop's response, Decoding Da Vinci, is to be published by Grove Books weeks before the film is released.

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