Hilary Duff at The Rodeo Drive Walk Of Style award in honour of Manolo Blahnik - Arrivals, Beverly Hills, California - 25.09.08

The pop star/actress has teamed up with America's Gay Lesbian + Straight Education Network to star in a new public service announcement.

In the ad, Duff swoops on two shopping teens when one of them describes a bad dress as "so gay," stating, "You know, you really shouldn't say that something's gay when you mean it's bad - it's insulting."

Duff says, "Nobody says it meaning to hurt someone's feelings but it can really make an impact on someone."

Source: WENN