Simon Cowell is known for his harsh criticism of pop wannabes

The Gay and Lesbian Alliance Against Defamation said it had raised concerns with broadcaster Fox over the remarks.

Cowell told a male contestant to "wear a dress" in the first episode of the fifth series, while fellow judge Randy Jackson asked one: "Are you a girl?"

The group said it was worried about the show's attitude to "gender expression".

"Last week we heard and voiced concerns about the 18 January edition of American Idol - specifically, the producers' decision to turn a contestant's gender expression into the butt of a joke," said spokesman Damon Romine.

"We've spoken with Fox and have entered into what we hope will be a productive, ongoing conversation about the show's representation and discussion of sexual orientation and gender expression."

Fox had no comment to make on the episode, which was watched by almost 36 million viewers.