Hollywood superstar Brad Pitt's representatives hit out at Vanity Fair magazine after it splashed semi-naked photos of the actor on the cover of its December issue.

The photos of Pitt -- shown standing in nothing but a pair of boxer shorts and a pair of socks -- were taken by artistic photographer Robert Wilson in September 2005, TMZ celebrity website said.

But while Pitt, 42, signed a legal release when the photograph was taken, he was oblivious they would end up on Vanity Fair's cover more than a year later.

"We are very disappointed that Vanity Fair has chosen to put an unauthorized cover on their magazine," a spokesperson for Pitt said. "It seriously makes me question their integrity and motives."

A statement from Vanity Fair said Pitt's managers had been notified on October 5 of the decision to use the photo for its special "art" issue.

The magazine defended the decision, saying it had obtained the right to use all Wilson's photographs taken as he put together a study of video portraits.

"Vanity Fair decided to do a story on Wilson's video portraits and obtained rights to the entire collection of photographs from those sittings, which included Pitt's," the statement quoted by TMZ said.

Vanity Fair has a long track record of publishing notable cover photos, most famously a shot of a heavily pregnant Demi Moore posing naked and more recently world exclusive shots of Tom Cruise's baby daughter Suri.