The Anti-Defamation League (ADL) said there had been "an outpouring of anti-Semitic comments on mainstream and extremist Web sites."

Madoff, 70, is Jewish and a prominent member of the powerful US Jewish community. He is alleged to have defrauded investors, including a number of Jewish-related charities, of some 50 billion dollars.

"Site users have posted comments ranging from deeply offensive stereotypical statements about Jews and money -- with some suggesting that only Jews could perpetrate a fraud on such a scale -- to conspiracy theories about Jews stealing money to benefit Israel," the ADL said in a statement.

"Jews are always a convenient scapegoat in times of crisis, but the Madoff scandal and the fact that so many of the defrauded investors are Jewish has created a perfect storm for the anti-Semites," said Abraham Foxman, ADL national director.

"Nowadays, the first place Jew-haters will go is to the Internet, where they can give voice to their hateful ideas without fear of repercussions."

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