"Christianity, the world's largest religion, is rapidly expanding - by all indications, its future is very bright," said Sir Diarmaid MacCulloch, professor of the History of the Church at Oxford University.
"But there are also many conflicts within it, and these are particularly serious in the Roman Catholic Church, which seems on the verge of a very great split over the Vatican's failure to listen to European Catholics."
The 60-year-old historian predicted that the Catholic Church faced a division over attempts by Popes John Paul II and Benedict XVI to "rewrite the story" of the Second Vatican Council by portraying it as a "minor adjustment" rather than as a "radical move to change the way authority was expressed".