Asda has failed to block an employment tribunal equal pay claim brought by more than 7000 workers at the supermarket.

The group - overwhelmingly women - work in hourly-paid jobs in its retail stores and want the same pay as comparators in the distribution depots, who are overwhelmingly men and paid substantially more.

Asda, which says there has been no discrimination and the claim should fail on its merits, wanted the employment tribunal to halt the proceedings, which would compel the employees to go to the High Court if they wished to fight on.

But the employment tribunal said it had no power to impose a stay and, even if it did, it would not be appropriate to do so.

Asda challenged that decision in the Court of Appeal and, on Wednesday, two judges ruled against the chain.

Its lawyers had argued that, although in most cases the employment tribunal was well suited to hear an equal value claim, the case was "highly exceptional, indeed unique" and that virtually all its aspects were disputed.

Giving the appeal court's ruling, Lord Justice Elias said that Asda's counsel, Lord Falconer, claimed it was the most important, complex, and financially significant equal pay claim ever pursued in the private sector which, if successful, would have an enormous effect not only on Asda and its 150,000 employees, but the retail trade generally.

Counsel also said there were very complex points of law and a High Court judge would be more suited to decide them.

Lord Justice Elias said that Parliament had recognised that in some circumstances the employment tribunal might be a more appropriate forum for determining an equal pay issue than the High Court - but it had not legislated for the converse and it was not for the tribunal to exercise its general powers to make good that omission.

That was particularly so given the potential prejudice to a claimant if that step was taken, such as the additional stress and court fees involved in starting proceedings again.

Very few High Court judges had experience in this field while a number of highly able employment tribunal judges did and had built up a degree of expertise.

An Asda spokesman said later: "The ruling from the Court of Appeal relates solely to the way the case will proceed in the courts - it has nothing to do with the merits of the case itself. Whilst we respect the Court's decision, we continue to strongly dispute the claims being made against us in the employment tribunal.

"This is a legal case about different rates of pay for different jobs. We believe that jobs in question are very different in terms of their demands, and we strongly dispute the claims being made.

"At Asda people doing the same job are paid the same. Men and women doing the same job in our retail stores are paid the same. Men and women doing the same job in our distribution and logistics centre are paid the same. Pay rates in stores and depots differ for legitimate reasons, including the different market rates for different jobs."