The OFT has written to Imperial Tobacco, Gallaher and British American Tobacco, to ask for copies of contracts with major retailers from supermarkets to high street chains.
The OFT said yesterday: "We have reasonable grounds to suspect a breach of the competition act.
"We have launched an investigation into price fixing in the tobacco trade. We have written to a number of tobacco manufacturers and retailers."
Imperial Tobacco, which makes Lambert & Butler and has a licence to distribute Marlboro cigarettes, said it had received a request for information from the OFT "concerning certain aspects of the UK tobacco supply chain". And that it had provided the information requested.