J Sainsbury has lost a legal battle on claims Tesco's Price Promise marketing campaign was misleading, unfair and unlawful.The UK supermarket complained that Tesco had unjustly compared its own-brand prices to Sainsbury's products.The group appealed a decision by Sir Hayden Philips, the Advertising Standards Authority (ASA) independent reviewer, that the both the grocer's products could be lawfully compared under UK Advertising Codes.Sainsbury's case against Tesco's campaign, which promises to match the cost of brand and own-brand products in rival supermarkets, was dismissed at London's High Court.Robin Terrell, managing director for Tesco in the UK, told staff in an email that he was "really pleased that the court has taken this decision"."We prefer talking to our customers rather than about the competition, so you won't hear us talking about this much publicly, but we should all be clear what it means," he added. "We know that at least nine out of 10 customers' Price Promise baskets are cheaper than Sainsbury's, and on the other one, we make up the difference."Sainsbury's said it was disappointed by the outcome and was considering its options."Whilst we respect the court's decision that the Independent Reviewer acted lawfully when adjudicating our complaint against Tesco, we continue to believe that it is fundamentally misleading for customers if price comparison schemes are inconsistent in taking into account provenance, quality and whether products are Fairtrade or sustainably sourced."These values continue to be at the heart of our business and it will be for customers to reach their own verdict on this issue."