An Orthodox rabbi has apologised for suggesting that some of the Jewish victims of alleged child sex abuse in Sydney two decades ago may have consented.

Rabbi Boruch Lesches, former senior Chabad leader and now head of the Lubavitch community in Monsey, New York, said he "deeply regretted" remarks made on a legally recorded phone conversation obtained by Fairfax media and uploaded on YouTube.

In the recording, Lesches admits that he knew about the abuse of a 11-year-old boy when he was living in Australia, but told the alleged abuser to stay away from him instead of going to the police with the information.

The rabbi also told the perpetrator that if the abuse did not stop, both he and the boy would be sent away from the community. Finally, he said that boys at Sydney's Yeshiva Centre may have consented to sex abuse.

"We are speaking about very young boys... everybody says about the other one that 'he agreed to this,'" Lesches said. When asked about young boys consenting, he said, "You would be surprised."

He defended his remark by saying that some non-Jewish boys, whom he called as "goyims," began acting or thinking sexually from as early as five years old. Teenagers from poor backgrounds also had "nothing else to do in life, only thinking 24 hours about sex" with each other, members of their own families, and even "dogs."

Lesches has apologised with a statement, saying that he "had no knowledge of the alleged charges claimed to have occurred some 25 years ago and discussed in the news report".

"I would like to apologise for statements made in a private telephone conversation that caused pain to the greater public.

"I am shocked to hear of these allegations, because I often entrusted my own young children to the care of the alleged perpetrator, without hesitation. I would never have done so had I known of the allegations," he said.

Orthodox Jewish Rabbi B. Lesches prays with some of the trainees from the Rabbinical College at the Yeshiva Synangogue in Sydney
Orthodox Jewish Rabbi B. Lesches prays with some of the trainees from the Rabbinical College at the Yeshiva Synangogue in Sydney (Reuters)