Hollywood stars Matt Damon and Michael Douglas have stripped nude to film a gay sex scene in the Liberace biopic, Behind the Candelabra.

The award-winning actors get into bed for a same-sex romp in the new trailer for the raunchy new HBO film about the legendary pianist.

In the two-minute promo, Douglas and Damon look almost unrecognisable as Liberace and his lover, chauffeur Scott Thorson.

Fans are treated to plenty of flesh in the preview as Fatal Attraction star Douglas plays Liberace, famed for his musical abilities as well as his flamboyant and extravagant lifestyle.

One clip shows the moment the star and his live-in lover meet backstage at the Las Vegas Hilton. Liberace hires Thorson as his chauffeur and hands over the keys to his crystal-encrusted Rolls Royce chariot.

In another scene, a toupee-clad Liberace tries to adopt his lover - before asking his plastic surgeon to turn Thorson into his lookalike.

Damon previously admitted that although they did not hold back in portraying the gay couple,filming the sex scenes was "awkward".

"The scene where I'm behind him and going at him - we did that in one take," he told Entertainment Weekly.

"We do it. Cut. There's a long pause. And then you just hear [director] Steven [Soderbergh] go, 'Well... I have no notes.'"

Behind The Candelabra is scheduled to air on HBO in the US on 27 May