The UK advertising watchdog has criticised two retailers for “misleading” consumers by advertising fashion items made from real animal fur as fake or “faux”.

The Advertising Standards Authority, in two separate rulings published on Wednesday, said a product listing for a pompom jumper by the online fashion retailer Boohoo and another for a pompom headband sold on Amazon by Zacharia Jewellers – both advertised as “faux fur” – had broken rules set by the Committee of Advertising Practice.

The items were spotted by the animal welfare charity Humane Society International in September as part of its ongoing investigation into the national problem of real fur being sold as faux across the UK.

The charity, which has been stepping up calls for a ban on UK fur sales, purchased the products and sent samples to an independent textile laboratory for testing, where both were confirmed to be real fur – most likely rabbit.

“Consumers should be able to trust the ads they see and hear – and they certainly shouldn’t be misled into buying a faux fur product in good conscience only for it to turn out to be from a real animal,” said Miles Lockwood, the ASA’s director of complaints.

“That’s not just misleading; it can also be deeply upsetting. Our rulings serve as an important notice to retailers and the clothing and textile industry about the need for truthfulness in their claims around faux fur products, and to get their house in order or face further action.”

Claire Bass, the executive director of HSI UK, said: “It’s completely unacceptable that compassionate consumers setting out to buy fake fur are being misled into buying animal fur.

“These two examples are the latest in a long list of ‘fake faux fur’ items we’ve found for sale, so we hope that the ASA’s rulings will send a strong message to the industry and make retailers work harder to give consumers confidence in avoiding cruel animal fur.”

Boohoo said: “We have a strong commitment against the sale of real fur in any of our products. We have robust policies and procedures in place to ensure that we are able to adhere to this.

“Following the inquiry by HSI the item has been removed from sale. We continue to investigate the matter internally and with the supplier in question, as a matter of priority.”

Zacharia Jewellers said it had been informed when it bought the products in China that they were faux fur. It has taken down the listing from Amazon and removed the product from its website.