The Co-operative Group has been accused of trying to create a monopoly after buying two rival stores in rural Northumberland and closing them down.
Councillors said the move would mean higher prices for shoppers in Seahouses and Belford and have complained to the OFT. They claimed restrictive covenants have been put on the stores, preventing them from being used for grocery.
The Co-operative Group bought the 1,450 sq ft Londis store in Seahouses in July, closed it down and moved staff to its nearby shop. The company has since bought the 1,500 sq ft Spar in Belford. It closed last week and, again, staff moved to the Co-opertaive Group's nearby store.
Campaigners claimed the move had left shoppers with the choice of using the Co-op stores or travelling 30 miles to Berwick or Alnwick.Geoff O'Connell, a parish councillor, said: "It's shameful that the Co-op is doing this. It is supposedly dedicated to fair trade yet here they have left their customers hostage to fortune."
A company spokeswoman defended its actions, adding that the Spar had not been trading well. "It was the owners who approached us. In Seahouses, again, we were approached by the owner and we acquired the business, securing the employment of the staff."