Smokers may have been overcharged for cigarettes after the Office of Fair Trading (OFT) accused two big tobacco companies and 11 retailers of alleged unlawful co-ordination of prices.

The OFT has issued a statement of objections detailing the charges against Gallaher, which makes the Silk Cut and Benson & Hedges brands, and Imperial Tobacco, whose brands include Lambert & Butler and Embassy.

The retailers that have been issued with a statement of objections include all four major supermarket groups: Tesco, J Sainsbury, Asda and Wm Morrison, as well as the Co-operative Group, the off-licence group First Quench, Shell, Somerfield and the convenience store groups T& S Stores and TM Retail.

The competition watchdog alleges that at various times between 2000 and 2003 these tobacco manufacturers and retailers made arrangements that restricted the ability of each retailer to determine its selling price independently.

This was achieved by linking the retail price of a manufacturer's brand to the retail price of a competing brand of another manufacturer.

In the case of Gallaher, Imperial Tobacco, Asda, Sainsbury, Shell, Somerfield and Tesco, the OFT also alleges that they indirectly exchanged information on proposed future retail prices.

Tesco immediately indicated that it would dispute the charges. A spokesman for the UK's biggest supermarket group said: "The OFT's investigation appears to centre on major tobacco companies.

"We do not believe that Tesco has acted in a way that has harmed consumers and we will make this clear to the OFT when we see the details of their allegations."

Sainsbury's also said it was confident of immunity after helping the OFT with its investigation. "Sainsbury’s has co-operated fully with the OFT since 2003 and, as a result, can expect total immunity from any potential resulting fines in the event the OFT concludes there has been an infringement," the supermarket group said in a statement.

John Fingleton, chief executive of the OFT, said: "For markets to work well for consumers, it is a fundamental principle that pricing decisions should be made independently.

"If we find evidence of anticompetitive activity, we are prepared to use the appropriate powers to punish the companies involved and to deter other businesses from taking part in such behaviour."

He added: "If proven, the alleged practices would amount to a serious breach of the law."

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