Blake Lively is threatening to sue any publication which reprints fake photos that claim to be the actress, 23, in the nude.
The shots were distributed across various websites on Tuesday evening.
In the pictures, a blonde woman is seen taking snaps of herself without any clothes on. But Lively's rep tells Us Weekly they are a complete hoax.
"The photos of Blake Lively which have just surfaced on various websites including Perez Hilton and Zap2it are 100 percent fake," her rep says.
"Blake has never taken nude photos of herself. Blake will pursue legal action against the publication which initially published these photographs and any other outlets that republish them in any manner."
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Lively's next film The Green Lantern hits cinemas on June 17.