Pope Benedict has rehabilitated a traditionalist bishop who denies the Holocaust, despite warnings from Jewish leaders that it would seriously harm Catholic-Jewish relations.
The pope issued a decree on Saturday lifting the excommunication of four traditionalist bishops who were thrown out of the Catholic Church in 1988 for being ordained without Vatican permission.
The four bishops lead the ultra-conservative Society of Saint Pius X (SSPX), which has about 600,000 members and rejected modernisations of Catholic worship and doctrine.
The Vatican said the excommunications were lifted after the bishops affirmed their willingness to accept Church teachings and papal authority.
In healing a 20-year-old schism that had wounded the Catholic Church, the decree looks set to spark one of the most serious crises in Catholic-Jewish relations in 50 years.
Israel's ambassador to the Vatican Mordechai Lewy told the Reuters news agency that "the eagerness to bring a Holocaust denier back into the Church will cast a shadow on relations between Jews and the Catholic Church."
One of the four bishops, the British-born Richard Williamson, has made a number of 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, he said "I believe there were no gas chambers" and only up to 300,000 Jews perished in Nazi concentration camps, instead of 6 million.
Asked about Richard Williamson's comments, chief Vatican spokesman Father Federico Lombardi said they were "totally extraneous" to the lifting of the excommunications.
Elan Steinberg, vice president of the American Gathering of Holocaust Survivors and their Descendants, said the Vatican had desecrated the memory of the victims when it should have taken their side.