Quinn Emanuel Urquhart & Sullivan is seeking judicial review to challenge the Competition Appeal Tribunal’s (CAT) decision in the £14bn Mastercard consumer claim.

The law firm had filed an application in August with the CAT to appeal, but has now taken its case to the Court of Appeal and High Court. An application has been filed with the latter by way of a judicial review.

Quinn Emanuel has been representing Walter Merricks CBE in the case, but saw its class action claim rejected by the CAT in July after it ruled the alleged losses suffered by 46 million British consumers caused by unlawfully high credit card fees could not be proven.

The judgment said that even if it were possible to determine the loss, the significance of the individual issues would mean that it is “impossible in this case to see how the payments to individuals could be determined on any reasonable basis”.

Quinn partner Boris Bronfentrinker is acting for Merricks and is instructing Monckton Chambers’ Paul Harris QC and Marie Demetriou QC, and Victoria Wakefield and Emma Mockford of Brick Court Chambers.

MasterCard is being defended by Freshfields Bruckhaus Deringer partners Jon Lawrence, Jonathan Isted, Nick Frey and Mark Sansom, instructing Brick Court’s Mark Hoskins QC, Tony Singla and Hugo Leith, and One Essex Court’s Matthew Cook.

Quinn Emanuel argues there is “legal uncertainty” over whether there is a direct right to challenge in the Court of Appeal or whether it needs to go to the High Court for a judicial review, so filings have been made in both courts.

The dispute arose following an infringement decision made against MasterCard by the European Commission over the corporation’s intercharge fees levied in 2015 and 2016 topped the list of The Lawyer’s Top 20 cases for 2017 and is the largest claim brought before the CAT.

Under the Consumer Rights Act of 2015, competition-related collective actions or class actions can be heard before the tribunal, meaning that individuals do not have to actively “opt in” to the action to receive legal representation’ on other words, they are automatically included in the claim unless they specially “opt out”.

Freshfields declined to comment.