The advertising regulator in the United Kingdom has banned two ads by Zara for using models who appeared "unheathily thin," finding the photos were "irresponsible" to run.

The Advertising Standards Authority (ASA) said staff investigated four ads the fashion retailer ran this May after receiving a complaint. It found two photos were in line with the U.K.'s standards, but two were not.

A ruling said styling choices for the photos — from the lighting of the image to the clothing itself — contributed to the impression that the model was overly thin.

"Her hair was styled in a slicked back bun, which drew emphasis to her head whilst making it appear slightly gaunt. There was a contrast in how her upper arms and elbow joints were positioned, which made her body appear slightly out of proportion. In addition, because of the style of dress she was wearing, the model's collarbone was visibly protruding," the ruling read.

"For those reasons, we considered that the styling, lighting of the image and the choice of clothing meant the ad created the impression that the model was unhealthily thin."

The watchdog ruled that the "irresponsible" ads cannot appear again in their current form and said Zara must ensure all its images are "prepared responsibly" moving forward.

The ruling said Zara has removed all the photos in question from its website after the complaint. The retailer said its models "had medical certification which proved they were in good health" when they were photographed.

It also said it had not altered the photos "beyond very minor lighting and colouring edits."

Previous bans

The fashion industry has been criticized for decades over its use of excessively thin models, which researchers have long linked to eating disorders, negative body image and body dysmorphia.

Other brands like Gucci, Urban Outfitters and Mango have also had ads banned over the issue. In 2015, the ASA banned an Yves Saint Laurent ad featuring a model whose ribcage was showing. 

Several countries have brought in protective measures over the years: France banned ultra-thin models without a doctor's note attesting to their health under a 2015 law, while Italy and Spain rely on voluntary codes of conduct.

Various fashion companies, individual publications and fashion weeks around the world have also restricted the use of underweight and underage models.