The Sunday Telegraph reported that Tesco, Asda, Sainsbury's and Morrisons were among companies targeted as part of an investigation into price fixing in groceries and health and beauty products.

The consumer watchdog is said to have seized hundreds of emails between retailers and their suppliers, who were apparently also visited, during Thursday's "surprise raids".

The OFT declined to comment. A spokeswoman said: "We never comment on investigations."

A Tesco spokeswoman said: "We understand that the OFT has asked for information from a wide range of suppliers and retailers. We are working with them to provide what they require.

"At Tesco we are confident that we always act in the interest of consumers. Indeed over the last 10 years we have saved the average family almost £5,000 as a result of our investment in price."

A spokesman for Asda said: "They came to our offices. They requested a range of information, and we were happy to assist."

A spokesman for Morrisons said: "I can confirm that they did visit us - along with many others - and we will be co-operating with them."

A spokeswoman for Sainsbury's said: "We are co-operating with the OFT. We have been asked for some information and we don't have any further knowledge of what their concerns are."

The development comes just two days after it emerged that 11 major retailers and two tobacco manufacturers are facing an OFT investigation over allegations of unlawful cigarette pricing practices.