An American Apparel advert has been banned by the UK's advertising watchdog over claims that it sexualised a model who appeared to be under 16.

The advert for the US company's Flex Fleece zip hoody, which appeared in Vice magazine, showed various pictures of a young-looking girl wearing the hoody and apparently naked underneath.

The Advertising Standards Authority (ASA) said that, although the model used in the ad was 23, she looked under 16 in some of the pictures and was gradually exposing more skin in the manner of stripping off for an amateur-style photo shoot.

"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," the ASA said in its ruling.

It said the ad could not appear again in its current form, but dismissed another complaint that the ad's nudity was offensive and unsuitable, as it could be seen by children.

The ASA said that the target audience and distribution of the magazine made it unlikely to be seen by children.

American Apparel told the ASA that the ad was designed to show that the hoody could be worn next to the skin, and was aimed at women.

The company "strongly refuted" the claim that the ad could be seen to sexualise a child.