HBO's hottest comic, Sacha Baron Cohen — best known as the goofy rapper Ali G. (search) — is in hot water for a gag-song he sang on TV that groups are calling anti-Semitic.

The British version of the FCC and the U.K.'s Jewish Board of Deputies are investigating Cohen for a phony Country-Western song called "Throw the Jew Down the Well" that he performed at a rural bar in Arizona for his show.

In the U.S., the sketch has also drawn fire from the Anti-Defamation League (search).

Cohen, who is Jewish, sang the song under the guise of Borat, a phony TV host from Kazakhstan, and soon the patrons at the bar were singing with him.

In the U.S., it aired on a recent episode of "Da Ali G Show," (search) a series in which Cohen hoodwinks unwitting guests into sometimes startling admissions with his in-depth portrayals of three different characters.

In this case, the Borat performance revealed a bar full of bigots on a hidden camera.

"While we understand this scene was an attempt to show how easily a group of ordinary people can be encouraged to join in an anti-Semitic chorus, we are concerned that the irony may have been lost on some of the audience, or worst still that they simply accepted Borat's statements about Jews at face value," The Anti-Defamation League's Abe Foxman told a reporter.

"It is a very thin line between what's offensive and what's supposed to be funny and that line was crossed," Foxman said.