By Matt Ayres
The consumer body Which? has called for action over "confusing and misleading" supermarket prices.
The group has launched a "super-complaint", a legal move which means the Competition and Markets Authority (CMA) must respond within 90 days.
Which? says it has repeatedly exposed the tactics, but remains frustrated that "dodgy offers" remain on the shelves.
However, the British Retail Consortium (BRC) has said it does not accept the implications of the complaint.
"The examples set out are very specific in nature and are not in any way indicative of broader systemic problems across the retail industry," said Tom Ironside of the BRC. "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."
Ironside did say the BRC would "examine closely the content of this super-complaint".
The main concerns identified by Which? are confusing and misleading special offers, lack of easily comparable prices because of the way unit pricing is being done and shrinking pack sizes without any corresponding price reduction.