A nude photo of Carla Bruni has been sold at an auction for $91,000 (£46,098). The picture of France's first lady has fetched more than 20 times the expected price.

The expensive photo depicts the ex-model standing in a pigeon-toed pose and covering her most private part of the body with her hands. The black-and-white photo was taken in 1993 by photographer Michel Comte during a period when Bruni was making a career as a model.

The bidder who won the auction has chosen to remain anonymous, but said he participated on behalf of a Chinese art collector, according to Christie's auction house in New York, which sold the photo.

The event caught the attention of French President Nicolas Sarkozy’s office, but there were no comment issued from that side. Mr Sarkozy married Ms Bruni in February, a few months after divorcing her wife Cecilia Ciganer-Albeniz.

The auction house was expecting to get between $3,000 and $4,000 (£1,519 and £2,025) for the photo that was auctioned as part of a sale of 140 photos from German collector Gert Elfering. The collection included work by Irving Penn, Richard Avedon, Helmut Newton and Peter Beard.

The media and the high “level of international interest for this photo" had played a key role in obtaining a high price for the Bruni photo, said Rik Pike, a spokesman for the auction house.

Another picture which fetched a high price was that of 1950s and 1960s French screen siren Brigitte Bardot. The auction was closed at $181,000, almost twice as expected, said Christie's auction. The collection of photos also included nude pictures of models Lauren Hutton, Gisele Bundchen and Kate Moss.

The money fetched through the sale of the photograph will go to Swiss charity Sodis, an organization which works to provide clean drinking water to developing countries.