The producers of Gossip Girl aren’t fans of folks Size 6 & up.

Actress Hilary Duff will appear as a guest star on several episodes of The CW’s R-rated young adult drama has already found herself on the receiving end of sharp tongue-lashing from show bosses, who have ordered the 21-year-old to get to work on dropping a few pounds.

Gossip Girl producers are reportedly concerned that the former star of Disney’s Lizzie McGuire isn’t waify enough to “fit in” with series skinny-minnies Blake Lively and Leighton Meester on the show’s New York City set.

A Star source says: “Hilary is fuming. She’s feeling insecure….”

Hilary Duff will play Olivia Burke, a famous film star in search of the normal college experience at New York University, when the third season of Gossip Girl premieres this fall.