Urban Outfitters has been forced by the UK's Advertising Standards Authority (ASA) to remove a photo of a model with a "thigh gap" from its website on the basis that the image is "irresponsible and harmful".
The image showed a model with a significant gap between her thighs, posing in a pair of "polka dot mesh briefs".
According to the Daily Mail, the ASA imposed the ban after receiving a complaint from an unnamed source.
The ASA – which regulates misleading, harmful or offensive advertisements – said: "The complainant, who believed that the model in the picture was unhealthily thin, challenged whether the ad was irresponsible and harmful.
"We considered that the model was very thin, and noted, in particular, that there was a significant gap between the model's thighs, and that her thighs and knees were a similar width."
It added: "We understood that Urban Outfitters' target market was young people and considered that using a noticeably underweight model was likely to impress upon that audience that the image was representative of the people who might wear Urban Outfitters' clothing, and as being something to aspire to. We therefore concluded that the ad was irresponsible."
Jo Swinson, the minister for women and equalities, supported the decision, and said it encouraged positive body image.
"Retailers will benefit from having a diverse range of models and mannequins which is not only a positive way of challenging low body confidence but makes good business sense too," Swinson said in a statement.
"Given the worrying rates of eating disorders especially among young people, I applaud the Advertising Standards Authority for encouraging positive body image, and for taking steps to ensure that retailers comply with this. I hope that Urban Outfitters remove these images, and that other retailers take note of these unacceptable images."
In response to the complaint, Urban Outfitters told the ASA that it did not believe the image was a problem.
It said it was "common practice to use slim models in the underwear industry", and that the firm "did not consider that the model was underweight or unhealthily thin".