The UK advertising watchdog has banned two ads by fashion giant Zara for featuring models who looked “unhealthily thin”.

The use of shadows and a slick back bun hairstyle in one ad for a short dress gave the model a “gaunt” appearance, said the Advertising Standards Authority (ASA).

The shadowing also made the model’s legs appear “noticeably thin”.

In the other advert, a model wearing an oversized pocket shirt revealed the model’s “protruding” collarbones, the regulator said.

The regulator described the adverts, shown on the retailer’s website and app, as “irresponsible”, and instructed Zara they must not appear again. 

Zara has pulled the images highlighted by the ASA inquiry. It said it had not received any complaints about them.

The company also said both models in the images had medical documents proving they were in good health when the photos were taken.

None of the images had been altered except for “very minor lighting and colouring edits”, Zara said.

The Spanish retail giant said it followed guidelines from a government backed inquiry into the health of models.

The ASA investigated two other Zara adverts but neither were banned.