A clothing firm has been criticised for using a model who looked under 16 in a "provocative" magazine advert.
The Advertising Standards Authority (ASA) ruled the shots for American Apparel "could be seen to sexualise a model who appeared to be a child".
In a series of six pictures, the model revealed more and more skin until her nipple was partially exposed.
American Apparel argued the model was 23 and the images showed how to use its clothing to create different looks.
The Los Angeles-based retailer has been banned from publishing the same advertisement again.
The initial shots showed the girl wearing just a hooded top and shorts with minimal make-up.
The ASA 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," said the ASA.
But it did not uphold a complaint from one reader who said the nudity was offensive and could have been seen by children.
The ASA noted 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".
High definition ruling
The independent watchdog made a similar ruling last year against a TV advert for the Oasis fruit drink, which showed a pregnant girl running away with her new "Cactus" boyfriend.
It found that while the girl was not under age, many viewers may have regarded her as being in her early teens. Viewers complained the adverts condoned teenage pregnancy and under-age sex.
Meanwhile, the ASA has also ruled that Sky advertisements that promised sports fans "every moment of the Ashes" in high-definition TV (HD) were misleading as some customers could not get the service installed in time.
Sky said it had recently trained more engineers and it was focusing on those areas where the waiting time was longest.
"Many customers were able to get installed in time for HD coverage of the Lions and Ashes and we're straight with customers by giving an estimated installation date before they buy," a spokesman said.