The major supermarkets face an unprecedented clampdown on their land-holding practices and could have their relationships with suppliers regulated by an independent ombudsman for the first time. The Sunday Telegraph, The Sunday Times, Daily Telegraph, Financial Times

The proposals form part of the initial findings of an 18-month probe by the Competition Commission into the £120bn sector to be published this week.

The regulator is expected to call for a shake-up of planning law to stop any of the big four supermarket chains seizing a dominant position in a local market.

The commission launched a probe into the supermarkets in May 2006. It will not publish its final report until next March.

Supermarkets will be particularly criticised for strategically holding or selling land in a way that could be anti-competitive. The commission will say that retailers who hold undeveloped land in towns where they are strong could be doing so with anti-competitive intent.

The commission will also seek to stamp out the use of “restrictive covenants”, a questionable practice under which supermarkets sell stores or land with the proviso that they are not used by other supermarkets.

The formation of a tough independent ombudsman to oversee supermarkets’ treatment of small suppliers and farmers will also be floated this week.