Sainsbury’s CEO Justin King today warned he is considering complaining to the ASA over Tesco’s new Price Promise initiative, describing it as unfair.

Tesco claims its price comparison tool, which launched last week, is more comprehensive than Sainsbury’s rival Brand Match because it compares own label as well as branded products.

But King claimed it was not possible for Tesco to compare like-for-like with its own-label products.

Asked by analysts at today’s results presentation if Sainsbury’s would consider extending Brand Match to cover such products, he said: “No, quite the reverse, actually. We think the strength of Brand Match is precisely that. That it is Brand Match. I think you have already seen some significant conversation around Tesco’s price match as to how on earth one truly and fairly compares own label. And of course we would share that concern.

“You can be sure we will be pointing out to Tesco where we believe their own-label products are being unfairly compared to ours” - Justin King, Sainsbury’s

“We think the vast majority of our Own Label is not comparable to that of our competitors and we know from our customer research that the reason they like Brand Match is that it is clear, straightforward, they know exactly what it is. Those brands are of course completely comparable supermarket to supermarket.”

King was asked if he would consider taking action against Tesco and if so, what options he had available.

“There is a new protocol that was agreed with the ASA about a year or so ago where the first place that you go, if someone is advertising something you think is unfair, you go to them,” King said. “So you can be sure we will be pointing out to Tesco where we believe their own-label products are being unfairly compared to ours.”

Tesco vigorously defended the methods it used for Price Promise, including web comparisons to prices at Sainsbury’s and Asda and physical checks at Morrisons stores.

“It is quite a lot of work for us to do, but we use clear guidelines to ensure the comparisons are fair,” said a spokeswoman. “Ultimately we do this because it’s what customers want us to do, given that approximately half of the average shopping basket in the UK is made up of own-label products.”