An ad for American Apparel's "back to school" range has been banned for "inappropriately sexualising" girls and potentially normalising predatory sexual behaviour.
The Advertising Standards Authority (ASA) said the two ads, which both showed the model photographed from behind from a low angle, imitated voyeuristic "up-skirt" shots which had been taken without the subject's consent or knowledge.
One showed the model wearing a skirt, top and white underwear bending over to touch the ground with her crotch and buttocks visible while the second showed her leaning into a car with her buttocks visible.
Two people complained that the ads were offensive and irresponsible because they were overtly sexual and inappropriate for a skirt advertised as schoolwear.
American Apparel said the model was a 30-year-old woman who was one of their photographers, and the ads did not and were not intended to represent an underage girl.
The images had been posted on the company's website and Instagram page by a junior and relatively inexperienced member of their social media team and had been removed for a variety of reasons after appearing only briefly, the company added.
It also denied that the images were part of any back to school campaign or marketing effort.
It defended the images, saying its approach was not graphic, explicit or pornographic - but featured models who were happy, relaxed and confident in expression and pose and were not portrayed in a vulnerable, negative or exploitative manner.
But the ASA said they model's head and upper body was obstructed, meaning that the focus was on her buttocks and groin rather than the skirt being modelled.
It said: "We considered the images were gratuitous and objectified women, and were therefore sexist and likely to cause serious and widespread offence.
"Furthermore, we considered the images imitated voyeuristic 'up-skirt' shots which had been taken without the subject's consent or knowledge which, in the context of an ad for a skirt marketed to young women, we considered had the potential to normalise a predatory sexual behaviour.
"We considered the ads had therefore not been prepared with a sense of responsibility to consumers or to society."
It also disputed American Apparel's assertion that the ads were not part of its school campaign, saying they featured in its "school days" or "BTS" - which it understood to stand for back to school - lookbook.
It also noted that it was not possible to determine the age of the model because her face was not visible.
The ASA said: "We considered that, from the context in which the ads appeared, it was likely that those who viewed them would understand that the model was, or was intended to appear to be, a schoolgirl.
"We considered the ads had the effect of inappropriately sexualising school-age girls and were therefore offensive and irresponsible for that reason too."
It ruled that the ads must not appear again in their current form.