AceShowbiz -

A never-before-seen picture of the late Princess Diana has just come to light. The image decreed "not to be published" features young Diana lying on a bed with a male friend, who is yet to be identified, reading a book nearby.

The photo, which is being marketed as a "salacious teenage image of the future princess," was believed to be taken on a Swiss ski holiday around 1979 or 1980, when Diana hadn't met Prince Charles. It was obtained by the Daily Mirror on February 26, 1981, two days after her engagement to the Prince of Wales was announced.

The picture remained in the paper's archive before it was bought by The Caren Archives seven years ago, and only surfaces because it's up for auction beginning January 17 by RR Auctions in New Hampshire.

Eric Caren, owner of The Caren Archive, tells the Daily Mail, "It's an intimate photo - I don't know the man in the picture and he could be a friend or a boyfriend." He adds, "This would certainly not be the way the Royal Family would have wanted Diana to be presented at that moment. Given that two days before her engagement had been announced."

"My guess is that it was a privately taken photograph that the Mirror purchased but for some reason did not publish," he further speculates. "Why the heck not I don't know - I don't know if it was pressure from the Royal family or an internal decision."