Relations between Jews and Catholics are under immense strain after a bishop made controversial remarks on his blog.

Richard Williamson, who has previously denied the existence of gas chambers and the murder of 6 million Jews during the Holocaust, accused the Jews of killing Jesus, a charge that divided the two faiths for centuries until Pope Benedict XVI declared this year that Jews could not be held responsible for Jesus's death.

In his weekly post, Williamson wrote that "the killing of Jesus was truly 'deicide' " and that "only the Jews (leaders and people) were the prime agents of the deicide because it is obvious from the gospels that the gentile most involved, Pontius Pilate, … would never have condemned Jesus to death had not the Jewish leaders roused the Jewish people to clamour for his crucifixion."

His comments have angered Jewish leaders and Holocaust survivors, who are urging Rome to cease reconciliation talks with the ultra-traditionalist splinter group to which Williamson belongs, the Society of St Pius X. Rabbi Pinchas Goldschmidt of the European Council of Rabbis said: "We call upon the Catholic church to suspend negotiations with extremist Catholic tendencies until it is clear that these groups show a clear commitment to tackling antisemitism within their ranks."

Last month, Régis de Cacqueray, the head of the French SSPX chapter, also accused Jews of deicide. To the despair of Jewish groups, there has been increased dialogue between the Vatican and SSPX.

Goldschmidt said: "Comments like these take us back decades to the dark days before there was a meaningful and mutually respectful dialogue between Jews and Roman Catholics. There must be no rapprochement within the Catholic church for those of its flock who seek to preach words of hate."

The Vatican has said SSPX will have to sign up to core teachings if they are to reintegrate, although it has not stated what these are. Four SSPX bishops, including Williamson, were excommunicated in 1988 when they were illegally ordained.

But the Vatican lifted Williamson's excommunication on the very day that his Holocaust-denying remarks were aired. The decision appalled Jewish leaders, with many suspending contact with the Vatican as a result. The Vatican said it did not know Williamson held such views.

Williamson has repeatedly ignored pleas to retract his remarks and not even the pope has managed to get the cleric to recant.

The fresh row will embarrass the pope, who is preparing to host a summit of world faith leaders in Assisi, Italy, next week as part of his interreligious outreach programme.