Sainsbury’s is to take the Advertising Standards Authority’s ruling over Tesco’s Price Promise to judicial review after claiming its own-label products are better quality than the competition.

Sainsbury’s commercial director Mike Coupe said the grocer will challenge the ASA decision because it is “fundamentally unfair”.

He said: “We do not believe that it is fair to compare own-label products. Our customers value our values position, and we are supported by organisations such as Fairtrade.

“We believe the quality of our own-label products are better than the immediate competition, and this is a position we feel strongly we need to protect.”

The ASA ruled in favour of Tesco in July following Sainsbury’s complaint.

Sainsbury’s alleged that  Tesco’s Price Promise – which launched in March, comparing the overall cost of a basket of its branded, own-label and fresh food against the same or equivalent products from Sainsbury’s, Asda and Morrisons – was misleading in relation to own-label and fresh food items because it did not take into account product attributes such as provenance and ethics.

Sainsbury’s own price mechanic, Brand Match, matches prices with the other grocers only on branded items.

Tesco UK marketing director David Wood said: “Sainsbury’s argument against Price Promise has been heard and rejected twice already. Tesco Price Promise offers customers reassurance on the price of their whole shop, in store and online, not just the big brand products.

“When family budgets are under pressure, that is the kind of help customers want and the real question for Sainsbury’s is why they aren’t trying to do the same for their customers.”

Coupe said the judicial review – which is likely to be heard in the High Court next summer – will include evidence about “hundreds, possibly thousands” of products. He gave the example of Sainsbury’s Basics water which is compared with Tesco’s Everyday Value water.

“Our water comes from a spring in Yorkshire, and this is being compared with water that comes from a tap. That isn’t a reasonable comparison,” Coupe said.

He said while quality is subjective, most of the evidence it will present is based on accreditation tests, “therefore it’s easier to see the difference”. He added: “The ruling doesn’t take into consideration whether a product is Fairtrade or MSC certified, but that does make a difference to our customers.”

The ASA said at the time of the ruling: “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.”

Wood said earlier this year on Tesco’s Price Promise: “A massive amount of work goes into making the comparisons, down to the quality of the individual ingredients, to make sure we make common-sense comparisons customers would see as fair and meaningful.

“The origin of a product can be important and where it is, for example Melton Mowbray pies, we compare by origin too. Where it isn’t a key factor for customers, we don’t let it stand in the way of making a common-sense comparison.”