The UK’s biggest supermarkets are resisting plans for an ombudsman to monitor the relationship between suppliers and retailers, according to a cross-party group of MPs.

The Grocery Market Action Group said contact with retailers revealed the ‘big four’ of Tesco, Sainsbury’s, Morrisons and Asda, as well as Iceland, did not back the scheme.

They said that introducing an ombudsman would hit customers by leading to increased food prices.

Only Waitrose, Marks and Spencer and Aldi have not oppose further regulation, claiming that good relationships with suppliers meant they had nothing to fear, the group found.

The group’s findings come as the Competition Commission’s 30-day consultation on its draft ombudsman proposal nears its end.

By next Thursday (28 May) supermarkets will have to give a formal indication of whether they intend to co-operate with the proposal to clamp down on unacceptable trading practices.

Without voluntary agreement from retailers, the Commission will have to refer the matter back to the government.

MP Andrew George, Grocery Marcket Action Group chairman, urged consumers to only shop at retailers that had proved to be serious about working with the Comission.

“While all the big chains are happy to promote themselves on the basis of their good relations with suppliers, only by accepting independent scrutiny can they prove that they are serious about fair dealing,” he said.

“Both consumers and suppliers stand to gain but the supermarkets will only change their position if their customers show they are only willing to give their money to retailers they can trust.”