The Revd Jay MacLeod, priest-in-charge of All Saints' church in Queen's Park, Bedford, conducted the experiment in which he compared the price of a basket of food at Tesco, and an equivalent one at local stores, after a Tesco Express opened in the town.
He rang up a devilish £81.94 at Tesco compared to a more saintly £69.08 at local stores.
MacLeod told C-Store that he hoped the stunt would induce shoppers to vote with their shopping baskets and use local stores more frequently.
"Using family-run shops not only saves money, it also keeps profits in the local community," he said.
He also slammed the new Tesco store for its promotion of self-scan tills. "Local shops are an important point of social contact in our area. Self-scan tills don't speak or listen, so if you fancy a chat at the checkout, you're better off at the locally-owned stores."