An imposter pretending to be Lindsay Lohan and Blake Lively's manager is wreaking havoc in New York - by booking parties and shopping sprees for the stars which never take place.

The man, calling himself Roy Cohen, has called exclusive Big Apple boutiques Prada and Gucci to request private store viewing sessions for Lohan and arranged a bash for Lively at the Empire Hotel.

But the New York Post claims neither actress showed up - and Lohan's publicist is dubbing Cohen a hoax.

Leslie Sloane Zelnick tells the newspaper, "He doesn't rep Lindsay or Blake and no one knows who the creep is."