If Pius XII was the first Nazi Pope, why does John Paul II want to turn him into a saint?

It's a big 'if'. But consider the evidence. The wartime pontiff ignored the Holocaust even though he knew about it as early as 1942. He failed to act over the round-up of more than 1,000 Roman Jews. His letters reveal him to be anti-Semitic. And, if the biographer who set out to clear him is right, he cut a deal with the Nazis to consolidate his position. So why is the current Holy Father hell-bent on his beatification?

On a trip to Africa last year, Pope John Paul II was asked what he thought of his predecessor Pius XII, the wartime pontiff. "He was a great Pope," he replied. Great enough, in fact, for the Vatican to be steaming full speed ahead to prepare Pius for sainthood.

On a trip to Africa last year, Pope John Paul II was asked what he thought of his predecessor Pius XII, the wartime pontiff. "He was a great Pope," he replied. Great enough, in fact, for the Vatican to be steaming full speed ahead to prepare Pius for sainthood.

There's another view of Pius XII, however: that he failed to condemn the most despicable crime of the century, the Holocaust. And those who hold this second view are shocked that the Pope has cast aside the misgivings of historians, Holocaust survivors, liberal Catholics and many inside the Vatican itself, and instructed two specialist "saint-makers" to sift through the voluminous evidence pointing to Pius's heroic virtues and prepare a special report postulating his beatification.

To say that the move is controversial is a gigantic understatement. Jewish scholars have worked overtime to unearth new documents indicating both a pattern of deathly silence and also opposition to the founding of Israel after the war. The Israeli government has begged the Vatican to delay the beatification process for at least 50 years out of deference to the Holocaust survivors.

So far, the Holy See has brushed off these misgivings with quiet confidence, upbraiding the Israelis for presuming to interfere in internal Roman Catholic affairs and pooh-poohing the accusations of complicity as a failure to appreciate Pius's diplomatic subtlety. If Pius said nothing about the Holocaust, the argument runs, it was because he could better protect the Jews under cover of silence. If he took care not to offend the Nazi dictatorship, it was to protect the integrity of the German Catholic Church at a time of virulent anti-religious sentiment.

That argument, however, may now have hit a dead end with the publication of a biography that provides startling new evidence of Pius's deep involvement in the rise of Nazism and points, among many other moral and political failings, to a virulent strain of anti-Semitism in the pontiff himself.

John Cornwell's book, entitled Hitler's Pope: The Secret History of Pius XII (Viking £20), is already the subject of fierce debate on both sides of the Atlantic. It is remarkable first because it taps hitherto unseen source materials inside the Vatican, and secondly because it is the work of an English Catholic who actually set out to exonerate Pius XII from the accusations hurled at him down the years.

Cornwell's determination to clear Pius's name gave him unprecedented access to archives lodged with the Jesuits and with the Vatican Secretariat of State. About halfway through his research, however, he fell into a state of moral shock. "The material I had gathered, taking the more extensive view of Pacelli's life [Eugenio Pacelli being Pius's given name], amounted not to an exoneration but to a wider indictment," he writes. "My research told the story of a bid for unprecedented papal power that by 1933 had drawn the Catholic Church into complicity with the darkest forces of the era."

We learn in greater detail how Pius prevented the publication of an encyclical commissioned by his dying predecessor to condemn Nazi anti-Semitism, how he avoided any specific mention of the Holocaust even though he knew about it as early as spring 1942, how he failed to speak out against the round-up of more than 1,000 Roman Jews in October 1943, and how many of the tales told over the past 50 years of his efforts to protect victims of Nazi persecution turn out to be exaggerated or entirely without foundation.

The story Cornwell tells is of a single-minded Vatican lawyer and diplomat who, from the earliest part of his career, set out to establish the absolute authority of Rome over Europe's Catholic populations in a series of accommodations with autocratic regimes. Having served as papal nuncio in Germany throughout the 1920s before becoming the Vatican's chief diplomat, Eugenio Pacelli was in a unique position to negotiate with the Nazis over the church's status. The deal that was cut guaranteed Catholic influence over education and spiritual life in Germany, but at a terrible price: the Catholic Centre Party was forced into dissolution, removing the last obstacle to Hitler's goal of absolute power, and all attempts at resistance by Germany's Catholic bishops were cut off at the knees.

The so-called Reichskonkordat, between the Vatican and Germany, handed the Nazis their first much-needed piece of international recognition and, according to Hitler's crowing at a subsequent cabinet meeting, opened the way to undertake "the urgent struggle against international Jewry". The concordat was celebrated in St Hedwig's cathedral in Berlin with swastikas flying alongside the Catholic banners and the "Horst Wessel" song, the Nazis' unofficial anthem, blaring out from loudspeakers to the thousands that had assembled outside.Cornwell shows that Pius XII's attitude to Jews was ambivalent at best, unearthing letters from his early career in Germany in which he refuses favours to the Jewish community on the most pusillanimous of grounds and describes the Munich chapter of the German Communist Party as being chaotic, filthy and full of Jews. He refers dismissively to "a group of young women, of dubious appearance, Jews like all the rest of them" and describes the Communist leader Max Levien as a Jew, "pale, dirty, with drugged eyes, hoarse voice, vulgar, repulsive..."

When, during the war, he came to learn of the extermination of millions of Jews, he made only the vaguest of references to the slaughter in a 1942 Christmas message - making no mention of either anti-Semitism or the Jews - and concentrated instead on developing his inner spirituality, commissioning a film called Pastor Angelicus to show off his reflective, fiercely ascetic nature."It is very sad," the then British ambassador to the Holy See, Francis D'Arcy Osborne, wrote in a letter unearthed by Cornwell. "The fact is that the moral authority of the Holy See, which Pius XI and his predecessors had built up into a world power, is now sadly reduced."

The Vatican has reacted to Cornwell's book with customary caution, tending to dismiss it without really engaging with its arguments. Pierre Blet, a French Jesuit who helped compile 12 volumes of papers supporting the case for Pius's papacy, dismissed Cornwell's research as ahistorical and asserted, unconvincingly, that the dissolution of the Centre Party could not have made a difference because Hitler was already in power.

Despite these cursory dismissals, the book is bound to be more troublesome than first reactions indicate. "Anything like this is a fly in the ointment because it ruffles the Vatican's desire to concentrate on the devotional aspects of the candidature for sainthood and forces it to re-examine history," said Giancarlo Zizola, a well-connected Catholic writer and historian. "The candidature is not ready yet, but I think it is quite likely there will be some kind of postponement."

All of this might be of strictly historical interest were it not for two related factors. One is the drive to make Pius a saint, which may or may not be in trouble; the other is the current state of the papacy. In many ways, Karol Wojtyla, the current Pope, has taken Pius XII as his model, rolling back many of the progressive developments of the Second Vatican Council to re-establish the Church as a highly centralised, autocratic body that brooks no dissent within its ranks.

Like Pius, Pope John Paul is virulently anti-Communist and has been far more willing to forgive the moral lapses of, say, right-wing governments in central America than he has those of Communist governments. Like Pius, this Pope has revived the cult of the Virgin Mary and places special significance in the Marian apparitions at Fatima in Portugal - an emphasis that appals intellectual Catholics as the triumph of mystification over rationality. The fact that the Pope is now championing Pius as a potential saint suggests that the Church has learned little or nothing from the ignominies of its past, despite its stated desire to admit its faults going back to the Inquisition.

Last year, the Vatican published a 14-page document entitled "We Remember: A Reflection on the Shoah", which was supposed to atone for the sins of the Catholic church against the Jews down the ages. Instead, though, it claimed anti-Semitism had nothing to do with the historical doctrines of the church, exonerated Pius XII and every other church leader or official, and blamed any lapses on the wayward "sons and daughters of the church".

"In the twilight years of John Paul II's long reign, the Catholic Church gives the pervasive impression of dysfunction," Cornwell writes. "At the outset of Christianity's third millennium it is clear that the Church of Pius XII is reasserting itself in countless ways, some of them obvious, some clandestine, but above all in confirmation of a pyramidal Church model - faith in the primacy of the man in the white robe dictating in solitude from the pinnacle."That model might yet prove dangerous, particularly if the omissions and collusions of Pius XII are given the official stamp of approval through sainthood. As the American author John Carroll, a specialist on Catholic- Jewish relations, writes in the latest issue of the Atlantic Monthly magazine: "Hitler's Pope makes it clear that if Pacelli is to be canonised now, the Church will have sealed its second millennium with a lie, and readied its third for new disasters."