The Court of Appeal has upheld a ruling that Asda store staff can compare their roles with those in the supermarket’s distribution centres.

The judgment follows an Employment Tribunal and Employment Appeal Tribunal against Asda’s attempts to – in the words of GMB workers’ union “block the legal claims of tens of thousands of workers”.

Represented by law firm Leigh Day, the staff argued that they should be paid equally to their colleagues in the retailer’s distribution centres.

A spokesperson for Asda has commented: “We are obviously disappointed with the decision, which relates to a preliminary issue of whether jobs in different parts of the business can be compared. Asda brought this appeal because it involved complex legal issues which have never been fully tested in the private sector and we will continue to ensure this case is given the legal scrutiny it deserves.

“We remain confident in our case. This appeal has caused no delay to the main case, which has been continuing in the employment tribunal. The tribunal has yet to consider whether the jobs are of equal value in terms of their demands; it is only if some jobs are of equal value that the tribunal will go on to consider the reasons for the pay differential between them, including the fact that there are different market rates in different industry sectors.

“At Asda, our hourly rates of pay in stores are the same for female and male colleagues and this is equally true in our depots. Pay rates in stores differ from pay rates in distribution centres because the demands of the jobs in stores and the jobs in distribution centres are very different; they operate in different market sectors and we pay the market rate in those sectors regardless of gender.”

Tim Roache, GMB general secretary, said: “We welcome this decision, we’ll always pursue justice and equality for our members and this decision is undoubtedly the right one.

“We know we’re not all the way there, there are more hurdles to jump in this process and as always we remain ready to negotiate should Asda want to get round the table.”