A political think tank is set to tell a parliamentary inquiry that the Office of Fair Trading has admitted that supermarkets could face a cap on their market share.

The New Economics Foundation will tell the All Party Parliamentary Small Shops Group High Street 2015 that OFT officials have acknowledged that a low market share limit is possible in law.

If such a law were invoked it would lead to the break-up of large supermarket chains. In 2000 the Competition Commission concluded in a report that an 8% market share was enough for supermarkets to abuse power over suppliers.