Mike Coupe, commercial director of the UK's third-biggest supermarket, said Tesco's Price Promise makes unfair comparisons between own-label products.
The Advertising Standards Agency (ASA) is set to rule on the issue on Wednesday, with reports suggesting the watchdog will side with Britain's biggest supermarket, Tesco, on the issue.
Sainsbury's, which has its own Brand Match scheme, argues it does not shy away from price comparisons on brands, but said comparing own brands is a different matter.
Mr Coupe said: "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.
"Well, it is obvious to us, and you'd have thought it would be obvious to Tesco."
Mr Coupe cited Tesco's comparison of the price of Sainsbury's Basics ham with its own Everyday Value ham. "They are priced the same but our pork is British and Tesco's is sourced from somewhere else in the EU," said Mr Coupe. "They're not the same product."
Tesco's Price Promise compares the price of goods in a shopper's trolley at the checkout with prices at Asda, Sainsbury's and Morrisons. It says any difference on comparable products is refunded to shoppers in a voucher worth up to £10.
A Tesco spokeswoman said: "We are confident that customers appreciate being able to make fair and transparent comparisons between supermarkets."
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