The Vatican ambassador to Israel threatened on Thursday to boycott a Holocaust memorial ceremony next week over a museum's portrayal of Pope Pius XII's conduct during the Nazis' killing of Jews in World War Two.

Archbishop Antonio Franco said he had written to the director of the Yad Vashem Holocaust Museum asking for the revision of a caption suggesting the wartime Pope had been apathetic to the Jews' plight.

The caption, quoted in the Israeli press, says Pope Pius XII "abstained from signing the Allied declaration condemning the extermination of the Jews" and "maintained his neutral position throughout the war".

Archbishop Franco said that in his letter he advised the Holocaust museum he "would not feel comfortable going to Yad Vashem" unless the wording was amended or the photo removed.