A website quoted Giacomo Babini, the emeritus bishop of Grosseto, as saying he believed a "Zionist attack" was behind the criticism, considering how "powerful and refined" the criticism is.
The comments, which have been denied by the bishop, follow a series of statements from Catholic churchmen alleging the existence of plots to weaken the church and Pope Benedict XVI.
Allegedly speaking to the Catholic website Pontifex, Babini, 81, was quoted as saying: "They do not want the church, they are its natural enemies. Deep down, historically speaking, the Jews are God killers."
The interview was spotted on Friday by the American Jewish Committee, which said Babini was using "slanderous stereotypes, which sadly evoke the worst Christian and Nazi propaganda prior to world war two".
On its website, the American Jewish Group Committee quoted bishop Vincenzo Paglia, an official at the Italian Bishops' Conference, as saying Babini's remarks were "entirely contrary to the official line and mainstream thought of the Catholic church".
As the interview appeared on Italy's main newspaper sites today, complete with the American reaction, the Bishops' Conference rushed out a statement quoting Babini denying he had ever given the interview in the first place. "Statements I have never made about our Jewish brothers have been attributed to me," he said.
Babini has previously been quoted on the Pontifex website accusing Jews of exploiting the Holocaust, as well as criticising homosexuality.
As cases of alleged priestly abuse emerge in the US and Europe, Benedict's handling of proven molesters before he became pope in 2005 has now been questioned in cases in Munich, Wisconsin and, most recently, in California, where his signature appears on an 1985 letter resisting calls to defrock a paedophile priest.