The OFT has already opened cases against companies in breach of pricing rules following the announcement of its market investigation on Thursday.

It urged retailers and other traders to review the use of common pricing mechanisms such as bogofs and time-limited offers in its final report on the advertising of prices.

The study ranked pricing practices in order of the potential detriment to the consumer. The worst are drip-pricing, time-limited offers and bait pricing. Reference pricing, volume and extra-free offers had less potential to mislead, the OFT said. Companies risk unlimited fines if they are found to be misleading consumers. "Pricing practices, used in a transparent and fair manner, can provide consumers with a helpful short cut to assess whether a particular offer is a good or bad deal. However, our research has highlighted how certain pricing tactics can be used in a misleading way," said OFT chief executive John Fingleton.

The BRC said honest retailers would not be concerned about the OFT's findings. "We take some reassurance that the OFT recognises that consumers understand reference and volume pricing," said Tom Ironside, director of business and regulation.