Supreme Court justices have unanimously upheld a ruling that so-called interchange fees charged by Visa and Mastercard restricted competition, in one of the largest cartel damages claims to be heard in English courts.

The case, brought by major retailers including Sainsbury’s, concerned whether multilateral interchange fees – paid by retailers for the processing of card transactions – restricted competition.

The Court of Appeal found in 2018 that the fee did infringe competition law and that all appeals should be remitted to the Competition Appeal Tribunal. In Sainsbury’s v Visa Europe Services and Sainsbury’s v Mastercard, five Supreme Court justices today upheld this conclusion, rejecting the card issuers’ appeal on all grounds bar one.

The court also allowed a cross appeal on the part of Asda, Argos and Morrisons, which argued that proceedings should not be remitted to the CAT on the question as to whether there is an exemptible level of interchange fees. Lord Reed, Lord Hodge, Lord Lloyd-Jones, Lord Sales and Lord Hamblen said Mastercard should not be allowed to re-open this issue, which it had lost after a full and fair trial.

Rob Murray, the Mishcon de Reya partner who represented Sainsbury’s, said: ‘We are pleased that the Supreme Court has ruled in favour of our client. This judgment not only confirms that the setting of MIFs is a restriction of competition, but it also sets out requirements for any possible exemption, and the test for whether any unlawful payment is pass-on to another party which may then have a claim.

‘This case will now provide guidance for the hundreds of other business claimants behind the lead cases, many of which are represented by this firm.’

Kate Pollock, head of competition litigation at Stewarts Law, which represented Argos, Asda and Morrisons, said: ‘The Supreme Court’s definitive finding on liability means that our clients’ claims can now proceed to trial on the issue of the quantum of damages. They look forward to a swift resolution of the matter without further delay.’

Last month, the Supreme Court was asked to consider whether collective action brought by 46 million consumers against Mastercard can proceed to the next stage of litigation. The card issuer is accused of overcharging UK customers in a case worth an estimated £14bn through its multilateral interchange fee scheme.