A nude photograph of Madonna is set to sell for thousands at auction next month.

The black and white picture, taken when the singer was 21, has been valued by Christie's at £7,000-£10,000.

Madonna was a struggling dancer in New York when she replied to a newspaper advert by celebrated US photographer Lee Friedlander who was looking for models for a series of nude photos.

Matthieu Humery, head of Christie's photography department, said the picture was "probably the most explicit" shot Friedlander took of the future pop icon.

He added: "For Friedlander it is a very typical way of taking pictures of a woman.
"He likes very natural women. There's not a hint of glamourising. That's what makes it powerful."

Friedlander said Madonna "seemed very confident, a street-wise girl" at the photo shoot.

He added: "She told me she was putting a band together but half the kids that age are doing that. She was a good, professional model."

She was paid just $25 (£17) for the picture but it was sold to Playboy for a much higher sum.

Another, later photo of the star, by Helmut Newton, is also up for auction, with a similar estimate of $10-15,000.

The auction takes place in New York on 12 February.

Other famous names whose portraits are for sale include Stephanie Seymour, Linda Evangelista, Joan Crawford and Lana Turner.