Moss was pregnant with her daughter Lila at the time

The almost life-size nude - entitled Naked Portrait 2002 - was painted while Moss was pregnant with her daughter.

The painting, which forms part of Christie's forthcoming Post-War and Contemporary art sale, is expected to fetch up to �3.4m.

A spokesman for Christies said it was the first time the painting had been shown publically.

'Ambition'

Moss herself originally suggested the posing for Freud in an article in Dazed and Confused magazine.

In the article she said one of her remaining ambitions was to pose for Freud.

It takes between six months and a year of regular sittings for the artist to complete a painting, but Moss said she was unconcerned by the length of time it would take.

Freud began painting in 2001 and started with Moss' slightly pregnant stomach so as to fix it in paint.

Naked Portrait 2002 - which was acquired by a private collector shortly after it was painted - will be auctioned on 9 February 2005.