Farmers have told the Competition Commission that the Office of Fair Trading should act as a police force in the grocery sector to ensure large retailers and manufacturers do not abuse their positions of power.

At the first of a series of personal hearings, part of the Commission's investigation into the UK's grocery sector, the National Farmers' Union said retailers should be forced to document all deals with suppliers and the OFT should carry out regular spot checks. It also argued that the OFT should adopt a proactive approach akin to that taken by the Food Standards Agency.

Robin Tapper, the NFU's head of food and farming, told The Grocer: "The FSA is responsible for making sure food law is carried out and it is very influential in promoting good practice."

At the hearing in London, on Tuesday, in the presence of Commission chairman Peter Freeman and two other members of the inquiry team, the NFU also maintained the OFT Supermarkets Code of Practice should include manufacturers as well as retailers.

Tapper said: "About 90% of our members deal with processors, not retailers, but in many ways the processors are just agents of the retailers. They simply try to claw back from their suppliers the cost pressures applied to them by their customers."

Next week, the Commission heads to Scotland for a series of hearings.