Some shops are failing to display prices as clearly as they should, the consumer watchdog has warned.
The Competition and Markets Authority says this could be preventing shoppers from being able to compare prices.
However, it said evidence suggests historically high food price inflation has not been driven by weak retail competition.
The CMA has written to shops who are failing to make pricing clear – and warned them to make necessary changes or risk facing enforcement action.
It has also asked the government to reform pricing legislation to help shoppers spot the best deals.