US retailer American Apparel has been accused of 'sexually suggestive and gratuitous imagery' after it used models who appear to be under the age of 16 in a selection of its adverts.

The high-street brand, which has been censured before for breaking advertising guidelines, posted a string of provocative ads on its website promoting tights and a range of coloured T-shirts.

In one of the adverts a woman only wearing a pair of high denier tights bends forwards with her back to the camera.

Another one shows "young-looking women" modelling a revealing shirt in different colours.

Both campaigns are said to have used exploitative images of young women, and have been banned by the Advertising Standards Agency (ASA) in the UK.

A probe was launched after the watchdog received a complaint from a mother who attempted to visit the website with her 12-year-old daughter.

She insisted that the more than 20 pictures in the stockings and hosiery section were "unnecessarily sexual and inappropriate for a website that could be seen by children".

Following an investigation, the ASA ruled that three of the 23 images used on the site were in breach of rules concerning "responsible advertising" plus "harm and offence".

An ASA spokesman said: "We considered the model looked under the age of 16.

"We acknowledged that her poses were not overtly sexual but, because her breasts were visible through her shirt, we considered the images could be seen to sexualise a model who appeared to be a child. We concluded the images were inappropriate and irresponsible."

The company, however, has defended the ad claiming that the ads of young girls in T-shirts were "completely decent and a fair representation of their product"

An American Apparel spokesperson insisted that its controversial campaigns were "standard practice" in the fashion industry.