Nigel Dowdney, owner of the Stalham Shopper store in the town, rejected Tesco's claim that the extension would bring more shoppers to the area and thus be good for the local economy.
Dowdney said: "Tesco said this when the store was built in 2002 but, in fact, the high street has been decimated."
He has called on fellow retailers to send him evidence of the impact such stores have had on other town centres. He added: "I would welcome evidence that this kind of store does revitalise local town centres, but I don't expect to find it."
Meanwhile, Tesco has dropped its appeal against Norwich City Council's decision to reject its controversial plans for a Tesco Express store on Unthank Road in the city, pending a fresh application. Bob Surridge, managing director of local chain Heads, said opponents to the plan would continue to keep a close eye on Tesco's next move.