By the standards of the internet, the photograph is relatively tame: an 18-year-old girl, standing in a bedroom in front of deep red curtains, pulling back her hair and smiling for the camera.

She’s stark naked, of course.

But this is a nude picture like no other. It could, in fact, represent one of the most expensive PR disasters in recent media history.

The naked girl is none other than Vanessa Hudgens, star of The Walt Disney Company’s hugely lucrative High School Musical franchise, which has generated an estimated $1 billion of operating profit for company over the past two years. The show, like Walt Disney itself, is as wholesome as children's entertainment gets: one of the reasons it has become such a cultural phenomenon.

Just to make things more difficult, the photograph was allegedly taken by Zac Efron, Hudgens’s 19-year-old boyfriend, and her co-star on the show. Together, the couple are by far the biggest “tween” stars in America, frequently appearing on the covers of celebrity magazines.

It is not known how the photograph ended up being published on the internet.

All this has left Walt Disney company – and its superstar chief executive, Bob Iger – with an impossible dilemma. If it supports Hudgens, will more nude pictures, some more explicit than the first, later emerge? And if it dumps Ms Hudgens, will fans dump the show?

So far, the company has chosen to back Hudgens, for fear of meddling with a proven formula, thus forcing parents across the country to have to explain to their children why their teen idol had disappeared from the screen.

High School Musical, about a group of teenagers putting on a show, was watched by 7.7 million people on its first showing in 2006, then a record for the Disney Channel.

This summer’s sequel attracted 17 million viewers, putting it at the top of the television ratings. The show has turned into a bonanza for Disney. It has spawned DVDs, soundtracks, books, video games, a concert tour, and even an exclusive line of Wal-Mart merchandise.

It also turned Bob Iger into a hero on Wall Street, where investors have been bidding up Walt Disney's stock price.

Having already produced a sequel, Disney has now “green-lit” a third instalment of High School Musical, due for release next year. However, contract negotiations for all the actors are still thought to be ongoing. “Vanessa has apologised for what was obviously a lapse in judgment,” said a spokeswoman for the Disney Channel, Patti McTeague. “We hope she's learned a valuable lesson.”

As for Hudgens, she told her fans this weekend: “I am embarrassed over this situation and regret having ever taken these photos. I am thankful for the support of my family and friends.”

In the show, Hudgens plays the part of the class swot, Gabriella. Her love interest is Troy, a basketball star played by Zac Efron. The fictional version of their romance is toned down by Walt Disney to the point where they barely kiss.

According to PR experts, Disney’s current strategy is the right one.

“What they shouldn't do is make a bigger deal out of it than is necessary," said Michael Levine, a Hollywood image consultant and author of 18 books. “The [nude] picture is not salacious.”

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