A landmark competition claim against Mastercard will be considered by the Supreme Court today via video link. Five judges will decide whether collective action brought by 46 million consumers can proceed to the next stage of litigation.

Mastercard is accused of overcharging UK customers in a case worth an estimated £14bn. The proceedings hinge on fees imposed by the card issuer on businesses that accepted its debit and credit cards between 1992 and 2008. The claim is brought on behalf of 46 million consumers by former financial services ombudsman Walter Merricks CBE.

An attempt to bring collective action was first made in 2017. However, the Competition Appeal Tribunal refused the application for a collective proceedings order (CPO). This decision was challenged by Merricks in the Court of Appeal in 2019. The court allowed the appeal, remitting the application for a CPO to the Competition Appeal Tribunal. The decision to remit the application will be appealed by Mastercard in the Supreme Court today.

Consumer champion Which? is expected to defend the collective action, addressing the court about the importance of the Consumer Rights Act 2015. Since the act was introduced five years ago, no claim has been allowed to proceed to a full trial.

Caroline Normand, director of advocacy, said: ‘Which? has long campaigned for a collective redress scheme, but with no claim under the new regime reaching a full trial, consumers have not yet had the results they need. This Supreme Court hearing is therefore a vital one for consumers and Which? has intervened to ensure the regime achieves its purpose of providing real access to justice.’

Last June, a US investment manager emerged as the backer of the case. Innsworth Litigation Funding, which is owned and funded by New York based Elliott Management Corp, is fully financing the £14bn damages claim - the biggest in UK legal history.