Consumer body Which? has urged the Competitions and Markets Authority (CMA) to put an end to "misleading" discounting from retailers.
The charity says that it has filed a 'super-complaint' with the regulator over "unfair and misleading pricing tactics" – the CMA now has 90 days to respond.
It claims that retailers are manipulating consumers into thinking that they are making savings with promotional items, when in fact shops are simply raising prices to offset any losses.
The consumer champion provided examples, such as Asda's multi-buy discount on Chicago Town Four Pizza Two-Pack. The standard price in 2014 was £1.50, which was raised to £2 before offering two packs for £3 – meaning that the customer has saved nothing on the original pricing. Asda returned the price to £1.50 when the promotion ended.
Kantar Worldpanel points out that 40% of groceries in the UK are sold on promotion.
Which? executive director Richard Lloyd said: "Despite Which? repeatedly exposing misleading and confusing pricing tactics, and calling for voluntary change by the retailers, these dodgy offers remain on numerous supermarket shelves. Shoppers think they're getting a bargain but in reality it's impossible for any consumer to know if they're genuinely getting a fair deal.
"We're saying enough is enough and using one of the most powerful legal weapons in our armoury to act on behalf of consumers by launching a super-complaint to the regulator. We want an end to misleading pricing tactics and for all retailers to use fair pricing that people can trust."
However, the British Retail Consortium rejected the criticism. Director of business and regulation, Tom Ironside, is quoted by the BBC as saying: "The examples set out are very specific in nature and are not in any way indicative of broader systemic problems across the retail industry.
"With thousands of products and special offers in store every day, errors may from time to time occur. However, these are rare in nature and are resolved quickly by the retailer concerned."