The Project Runway mentor was asked whether he thought Jersey Shore or Real Housewives was a "worse influence on style" during an appearance on Lopez Tonight.
Gunn said: "Let me put it this way, at least the housewives - absence of taste level or not - make an attempt to dress up. The Jersey Shore people, what is that?!"
After being shown a cast photo for Jersey Shore's upcoming fourth season, he said: "It's all that stretch material: the spandex, the lurex, the tightness, the skin. It's vulgar, I'm sorry."
Gunn then spotted that Snooki was wearing thigh-high leopard print boots with her leopard print dress: "And what is Snooki wearing on her legs?!"
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George Lopez asked Gunn if he considered Snooki, real name Nicole Polizzi, to be a "fashion icon", promoting Gunn to laugh: "If Snooki is a fashion icon then I am leaving the industry! Not even remotely!"
Gunn can be seen in upcoming movie The Smurfs and the new season of Project Runway, which premieres this Thursday at 9pm ET/PT on Lifetime.
Snooki is currently filming the fifth season of Jersey Shore in Seaside Heights, following the cast's return from Italy where they shot the fourth season.
Jersey Shore returns to MTV on August 10 at 10pm.
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Watch a trailer for Jersey Shore's new season below:
Watch a trailer for the new Smurfs movie below: