A model featured partially nude in a "provocative" fashion advert looked under 16, the advertising watchdog ruled today.
The shots for trendy Los Angeles-based retailer American Apparel showed the girl wearing just a hooded top and shorts with minimal make-up.
In each picture she progressively revealed more skin until the final frame in which she wore the fleece unzipped with her nipple partially exposed.
American Apparel argued that the model was 23 and the six images showed how to use the top to create different looks.
But the Advertising Standards Agency decided "the photographs suggested that she was stripping off for an amateur-style photo shoot".
It also ruled that she appeared under 16 in some of the shots.
"Because the ad could be seen to sexualise a model who appeared to be a child, under the age of 16 years, we concluded that it was inappropriate and could cause serious offence to some readers."
But it did not uphold the claim of the one person who complained that the nudity was offensive and could have been seen by children.
The ASA noted that the advertisement was published in a magazine called Vice which is aimed at the 18-34 market and distributed free in bars, nightclubs and clothes shops.
It ruled the nudity "was not so overly gratuitous as to make it unsuitable for or likely to cause serious or widespread offence to the target audience".
American Apparel have been banned from publishing the same advertisement again.
American Apparel's UK operations manager Brent Chase said: "American Apparel is well known for its provocative advertisements.
"Our models are real girls who are often employees or friends of the company. They do their own hair and make-up and aren't Photoshopped. From time to time people are made uncomfortable by this, and it occasionally causes an unfortunate reaction."
A spokesman for the company added that it only places its advertising in appropriate publications and said that the target readership of Vice reflected American Apparel's customer base.
He added: "American Apparel currently advertises in 20 different countries, rarely resulting in complaints from their respective advertising standards bodies, and this inquiry is one of those sporadic instances."Reuse content