Sainsbury's made a formal complaint to the Advertising Standards Authority (ASA) about Tesco's money-back pledge, claiming that it misled consumers because it did not take "important product attributes" into account.
The scheme compares the price of goods in a shopper's trolley at the checkout with prices at Asda, Sainsbury's and Morrisons, with any difference on comparable products refunded in the form of a voucher worth up to £10.
But ahead of the ASA's ruling, Sainsbury's commercial director Mike Coupe said the Price Promise made unfair comparisons between own-label products, citing its own Basics ham produced from British pork and the Tesco Everyday Value equivalent "sourced from somewhere else in the EU".
Mr Coupe said: "They are priced the same but our pork is British and Tesco's is sourced from somewhere else in the EU. They're not the same product. If there's one big lesson that we should all have learned from the horsemeat scandal, it's that customers care deeply about where their food comes from and how it is produced."
Tesco said that for differences such as provenance or ethics, they would still match products providing the distinction was not "key" in a customer's decision-making process. However, where an element like provenance was a factor, such as for Melton Mowbray pork pies, they price-matched on a like-for-like basis.
Rejecting Sainsbury's complaint, the ASA said rules required advertisers to compare goods which met the same need or intended purposes.
It said: "We considered the 'same need' test had been met under the code given that food such as meat, eggs or fish were interchangeable and were intended for the same purpose.
"While we acknowledged there would be differences in animal welfare and country of origin for the ingredients, we were satisfied that Tesco had taken those elements into account when identifying and matching products and had compared on the basis of them meeting the same need."
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