Supermarket Asda is waiting for the latest ruling in a long-running legal battle by its staff over equal pay.

The retail giant is challenging an Employment Appeal Tribunal (EAT) decision that jobs in Asda stores are comparable to those in the firm’s distribution centres.

At the Court of Appeal in London on Thursday, senior judges ruled on a separate preliminary issue relating to two groups of claimants who issued their legal actions against Asda together.

The court decided that one group of claims brought against the company could proceed in the employment tribunal despite being issued irregularly, but upheld the decision to strike out another group of claims against the supermarket.

The Court of Appeal is expected to rule at a later date yet to be fixed on whether the jobs of Asda retail workers – mostly women – are comparable to those working in the supermarket’s depots.

However, even if Asda loses at that stage of the litigation, workers will still have to demonstrate that the roles are of equal value and, if they are, that there is not a reason other than sex discrimination which means the roles should not be paid equally.

Law firm Leigh Day, which says it represents more than 27,000 Asda shop floor workers, as well as staff at Sainsbury’s, Tesco and Morrisons, estimates the total value of the claims against the big four supermarkets, if they lose their cases and are ordered to pay all eligible staff, could be more than £8 billion.