Its 'emerging thinking' document has been published today (Tuesday) but the full report is not expected until next year.

So far, the CC has looked at the supply chain, planning and land banks.

Inquiry group chairman Peter Freeman said:

"Our principal concern now is to focus on competition between retailers at the local level, where it matters most to consumers, as this is where many of the potential concerns we have would be evident."

He said the inquiry was not looking to "punish success or individual retailers".

But he added:

"We are concerned whether Tesco, or any other supermarket, can get into such a strong position, either locally or nationally, that no other retailer can compete effectively."

The interim report raised concerns about farmers and said that it had not received as much specific evidence about the unfair treatment of suppliers as it had expected.