An advert from the fashion retailer PrettyLittleThing has been banned by the Advertising Standards Authority (ASA) due to using “socially irresponsible” images of a 16-year-old model that depicted her in a sexual manner.

The ASA said the retailer highlighted Alabama Barker’s young age while featuring her in a series of sexually suggestive poses and clothing.

The images appeared on the retailer’s website in June, with brand ambassador Barker modelling her Y2K Edit clothing collection.

Text on the advert said: “Channel that teen dream realness with barely-there micro mini skirts,” while a series of images showed Barker wearing a tight-fitting short dress while sucking a lollipop, wearing high heels and a low-cut short dress that revealed her breasts while spraying a water hose, clutching her chest with one hand, and posing with her leg bent wearing a mini skirt and knee-high boots.

One page said: “Nail the latest trends and team a cropped varsity jacket with a mini skirt and knee-high boots for a date with your best dolls or flaunt your curves in a white figure-hugging dress.”

A complainant, who believed Barker was 16, challenged whether the ad breached advertising regulations by portraying someone who was under 18 in a sexual way.

PrettyLittleThing confirmed that Barker was 16 when the ad was made and said it wanted to convey a message of body positivity to encourage and empower young women to embrace their bodies and inspire confidence.

The firm said it did not intend to sexualise Barker and disagreed that she was portrayed in a sexual manner, adding that the ad was approved by Barker and she was posed in a similar style to images on her own Instagram account.

Upholding the complaint, the ASA said a number of Barker’s poses and text references were likely to be considered as sexual while the phrase “channel that teen dream realness” further highlighted her young age.

The watchdog said: “Given the above, we considered that the ad depicted a person who was under 18 in a sexual way, and we therefore concluded it was irresponsible and breached the code.”

It ruled that the ad must not appear in its current form, adding: “We told PrettyLittleThing to ensure future ads did not include images that portrayed or represented anyone who was, or seemed to be, under 18 in a sexual manner.”

PrettyLittleThing declined to comment further on the ruling.