Sainsbury's commercial director Mike Coupe said it was "time to take a stand" on the row over the Tesco Price Promise, which the supermarket believes does not offer a fair comparison.
Mr Coupe said:
"Tesco says that whether, for example, a product is Fairtrade or MSC [Marine Stewardship Council] certified is just a 'minor part' of a customer's considerations - especially for value products. We disagree.
More than ever, customers want to let their values guide them and in price-matching its products with ours, Tesco is - when it sees fit - choosing to ignore factors such as ethical or provenance certification or even country of origin.