Pop-up adverts offering customers cashback on websites of companies such as Asda and Domino’s Pizza have been banned by the advertising watchdog.

The Advertising Standards Authority (ASA) found a number of adverts by Webloyalty, which runs shopper reward programmes, to be misleading.

The pop-ups appeared after a customer had purchased an item online, offering them cashback worth about £20.

Text on the adverts said shoppers can click on a link “to claim the above reward, credited on to your card, when you next place an order” with the retailer.

Smaller text underneath a “continue” button read: “By tapping above, you can join our partner programme for £18/month and claim your reward.”

The adverts investigated by the watchdog appeared on the websites of retailers Domino’s Pizza, Papa Johns, Moonpig, Asda and Trainline.

The ASA said it was not clear to customers the pop-ups were coming from a third party, and that by clicking “continue” some people would have thought they were finalising their transaction with the retailer.

Consumers may also have been led to believe they had earned a free cashback reward based on the order they had just placed.

The ASA said this was not the case, and therefore found the adverts were likely to mislead people.

Webloyalty said it felt it was clear to shoppers their order with the partner website was complete, that the pop-ups were offered by a third-party service, and that it was advertising signing up for a paid-for scheme.

The ASA’s rulings mean the adverts, in their current form, are banned and Webloyalty must make future marketing communications clearer for shoppers.

The retailers which host the adverts must also ensure they are clearly seen as coming from a third-party subscription scheme, ASA said.

A spokeswoman for Webloyalty said: “As part of a wider piece of industry work on online choice architecture, the ASA reviewed some of our advertisements for our cashback savings programme.

“We have previously and proactively been liaising in a co-operative manner with advertising bodies, including the ASA and the CAP (Committee of Advertising Practice) copy advice team, to ensure our ads comply with UK advertising standards.”

Webloyalty said it had “already amended our marketing to make our messaging even clearer” prior to the ruling and “will continue to work to ensure our communications align” with ASA’s standards.