Pope Benedict's rehabilitation of four traditionalist bishops may heal one festering Catholic wound at the expense of opening a wider one with Jews because one of the prelates is a Holocaust denier.

The four bishops re-admitted to the Church over the weekend lead the far-right Society of Saint Pius X (SSPX), which has about 600,000 members and rejects modernisations of Roman Catholic worship and doctrine.

One of the four, the British-born Richard Williamson, has made statements denying the full extent of the Nazi Holocaust of European Jews, as accepted by mainstream historians.

In comments to Swedish television broadcast on Wednesday and widely available on the Internet, Williamson said "I believe there were no gas chambers" and only up to 300,000 Jews perished in Nazi concentration camps, instead of 6 million.

"I believe that the historical evidence is hugely against 6 million having been deliberately gassed in gas chambers as a deliberate policy of Adolf Hitler," he said.

While lifting excommunications that had barred them from the Roman Catholic Church left many internal questions open, there was no doubt it has provoked what some are calling the biggest setback in Catholic-Jewish relations in half a century.

Israel-based Rabbi David Rosen, head of inter-religious affairs for the American Jewish Committee and a leading figure in decades of dialogue with the Vatican, said:

"The late Pope John Paul II called anti-Semitism a sin against God and man. The denial of the overwhelmingly detailed documentation of the Shoah (Holocaust) is anti-Semitism at its most blatant.

"In welcoming an open Holocaust denier into the Catholic Church without any recantation on his part, the Vatican has made a mockery of John Paul II's moving and impressive repudiation and condemnation of anti-Semitism," he said.

Elan Steinberg, vice president of the American Gathering of Holocaust Survivors and their Descendants, spoke of "an act of moral debasement unworthy of a moral institution".

Abe Foxman of the Anti-Defamation League said: "What was the imperative to bring these people back into the Church at such a high cost to the Jewish people?"

Diplomatic sources said the row could put the pope's planned trip to the Holy Land in May in doubt.

A Vatican spokesman said that while Williamson's comments are "open to criticism" they were "totally extraneous" to the lifting of the excommunications.

But Jewish leaders did not accept the explanation. They questioned why the Vatican had not issued a clear statement condemning Williamson and one said privately the decree represented "a nail in the coffin of 50 years of dialogue".

Catholic-Jewish relations were already severely strained over the figure of wartime Pope Pius XII, who Jews have accused of turning a blind eye to the Holocaust. Jews have asked the Vatican, which denies the charges, to freeze the procedure that can lead to his sainthood pending more study of wartime records.

ENDING A SCHISM?

The rehabilitations of the four bishops followed years of negotiations with the Vatican to return to the fold.

They have won some battles, such as a wider use of the Latin Mass, as Benedict has sought to end a schism that pierced the Church's unity 20 years ago when French Archbishop Marcel Lefebvre ordained the four without a papal nod.

Their leader, Bishop Bernard Fellay, said, "Catholics attached to tradition throughout the world will no longer be unjustly stigmatised". He said the group was ready to help the pope "remedy the unprecedented crisis that currently shakes the Catholic world".

But Fellay made it clear they still had "some reservations" about the teachings of the Second Vatican Council (1962-1965), which modernised the Church and is accepted by most of its 1.1 billion members, as opposed to the 600,000 traditionalists.

Paris Cardinal Andre Vingt-Trois called the pope's decision "a measure of clemency and mercy" that would allow the Church to repair a damaging split but said it was a first step towards total re-integration and indicated the SSPX would have to bend to Church discipline.