JOAQUIN PHOENIX's publicist has fired back at reports the actor's rap career is all part of a prank, insisting the WALK THE LINE star really has big music plans.

Pals close to the star claimed earlier this week that Phoenix's recent shambolic performance in a Las Vegas nightclub, which was caught on film by brother-in-law CASEY AFFLECK, was all part of an elaborate "art project" hoax.

But his representative, Susan Patricola, insists the actor's rap plans are genuine - and he really has retired from movies to focus on a music career.

She tells MTV News, "He intends on exploring his musical interests, despite speculative, negative or positive reactions."