Mike Coppola/Getty Images

Once again, Joan Rivers is in hot water over a joke she made about Nazi Germany and the Holocaust.

Commenting on German model Heidi Klum's daring Oscar party dress on E!'s "Fashion Police" Monday, the 79-year-old comedian cracked: "The last time a German looked this hot was when they were pushing Jews into the ovens."

Rivers, herself Jewish, then doubled over with laughter.

Maury Phillips/Getty Images

Anti-Defamation League director Abraham Foxman quickly condemned Rivers' remark.

"Of all people, Joan Rivers should know better. This remark is so vulgar and offensive to Jews and Holocaust survivors, and indeed to all Americans, that we cannot believe it made it to the airwaves," Foxman said in a statement on the ADL website. "Making it worse, not one of her co-hosts made any effort to respond or to condemn this hideous statement, leaving it hanging out there and giving it added legitimacy through their silence.

"Almost as bad as her original comment is the fact that she sat there doubled over with laughter after saying it," Foxman added.

Rivers, however, refuses to apologize.

In a statement to ABCNews.com, she said, "My husband lost the majority of his family at Auschwitz, and I can assure you that I have always made it a point to remind people of the Holocaust through humor."

Klum has yet to comment on Rivers' remark. Her rep did not respond immediately to ABCNews.com's request for comment.

Rivers ran afoul of the ADL last year, while protesting Costco's decision not to carry her book, "I Hate Everything …S tarting With Me." She compared the retailer to Nazi Germany.

Read More About Joan Rivers' Costco Protest

"Germany is where banning books started, and it can start here just as quickly," she said at the time.

After she was criticized, Rivers quipped, "Don't talk to me about the Holocaust!"