Major supermarkets are under official investigation after it emerged that questionable special offers encouraged shoppers to spend, not save.

Consumer group Which? has launched a "super complaint" and demanded action from supermarkets. It found that shoppers are confused by special offers in supermarkets and spend £1,300 more a year when they are in place. The deals could now be banned within weeks under a clampdown being prepared by The Competition and Markets Authority (CMA), as research revealed such deals were "seducing" shoppers into spending more. 

The CMA’s investigation will look into unlawful pricing and promotional practices, which are designed to encourage customers to spend more.

Among the questionable deals condemned were multi-buy offers that didn’t reflect a real saving, and reductions based on a false previous price.

A spokesman for the British Retail Consortium, which represents supermarkets, said: "UK retailers are committed to treating their customers fairly and to avoid misleading them in any way.

"Millions of shoppers across the country enjoy the benefits of price promotions and special offers. Recent research has shown that, with the exception of fruit and vegetables, food prices in British supermarkets are on average 7% lower than the Eurozone average.

Clearer and simpler

“In addition, major supermarkets have worked with government and public bodies to make pricing clearer and simpler for customers, such as improving the way that unit price is displayed."

A report into the findings of the investigation is expected to be published next month.