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.
More top news
One group of women, each with children who died in Syria after becoming radicalised, told ITV they "still live every day wondering" why?
We've not seen such widespread cold so late in April for over three decades and in the next 24 hours more sleet and snow to come.
A man in a panda onesie has been shot after allegedly making a bomb threat against a television station.