Supermarket Sainsbury's has won the right to a judicial review in its fight against rival Tesco's Price Promise campaign.
The grocery chain is challenging a ruling by the Advertising Standards Authority (ASA) that rejected its complaint over the Tesco pledge.
Sainsbury's lost an appeal against the ASA decision in October, when a report by the watchdog's independent reviewer Sir Hayden Philips backed the ASA findings.
But the supermarket said it has been granted leave by the High Court to proceed with a judicial review.
The Tesco money-back pledge 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.
Sainsbury's believes it misleads consumers because it does not make fair comparisons, by for example, matching products such as its Everyday Value Tea, which is not Fairtrade, with Sainsbury's basics tea, which is.
It added the pledge is also misleading on its basics water, which comes from a spring in Yorkshire, and is compared with Tesco's Everyday Value water, which Sainsbury's claims starts at the mains supply.
"Our customers value our values. We strongly believe the quality of our own-label products is better than the immediate competition and this is a position we will fight strongly to protect.
"Values are fundamental to the way we do business and drive everything we do. We know these values matter to our customers and we will do everything in our power to ensure they can make informed choices about what they buy."
The case will now proceed to a formal hearing in around six months.