Sainsbury's has threatened rival Tesco with legal action over a dispute involving price comparison adverts.
Officials at Sainsbury's are requesting a judicial review into the Advertising Standards Authority's (ASA) verdict that Tesco's Price Promise campaign broke rules, according to the BBC.
Executives had originally argued Tesco's campaign misled consumers by ignoring differences in quality and the features of its own-brand products. Tesco and the ASA rejected this claim, with the former stating it is "offering the kind of help customers want".
The Tesco promotion in question compares the price of products that customers buy and then refunds the difference via a voucher.
But Sainsbury's is adamant that this is misleading and points out that while Tesco's Everyday Value teabags are cheaper than its own Basic range, it's variety has a Fair Trade accreditation and this means it is more valuable to consumers than Tesco's teabags.
Mike Coupe, Sainsbury's commercial director, said: "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."
Tesco marketing director David Wood countered by stating: "Tesco Price Promise offers customers reassurance on the price of their whole shop, in store and online, not just the big brand products."
But while this battle rages on, there have been consumer complaints that none of the big supermarket chains, including Asda, include rising grocer Aldi in their comparisons - with some believing the German company offers better value.
While Asda and Tesco offer more direct price comparisons, Sainsbury's only does this for branded products.
Any judicial review into price comparisons could potentially prove costly for the losing party with the trial providing a very public demonstration of which supermarkets provide the best deals and which are lagging behind in this regard.
By Francesca Witney