Supermarket giant Asda, part-owned by Blackburn billionaire Mohsin Issa, faces a major equal pay claim today as 60,000 workers take their case to an employment tribunal.

The workers are taking the largest ever private sector equal pay claim against the supermarket, with demonstrations being held in Manchester – where the case begins today (Monday) – and in Brighton at the TUC Congress.

The case, which is expected to last three months, centres on the retail workforce being paid up to £3.74 less per hour than the warehouse workforce.

The GMB Union says the retail staff are predominantly women, while the warehouse staff are predominantly male.

Claimants will argue retail work is of the same value as warehouse work, so they should be paid the same.

If the claim is successful, the union believes the decision could cost Asda billions of pounds.

The tribunal follows a recent decision at employment tribunal for fashion retailer Next, which lost an equal pay battle.

Its shop sales staff are paid less than warehouse workers, again with a similar gender divide to the Asda case, and the tribunal ruled Next had failed to show this was not sex discrimination.

Next had said the market wage for warehouse work was greater than that of shop workers and gender was not a factor, but the tribunal said this was not a lawful defence where the workforces are doing “equal work”.

Leigh Day, which represented Next staff in their claim, is also taking the fight to Asda for its staff.

Lauren Lougheed, Leigh Day partner, said: “The equal pay team at Leigh Day is very encouraged by the huge success we experienced just last week on behalf of the many thousands of women we represent who have been fighting for equal pay at Next. 

“We hope we will also be successful in the parallel claim we are bringing on behalf of more than 60,000 clients against Asda. 

“If we win at this Stage 3 hearing, Asda will then have to prove that there is a genuine reason for the pay difference between store workers and warehouse workers which is not based on sex.

“Next bosses failed to do this and our clients won. We are confident that the same will be true in the Asda claim.”

Nadine Houghton, GMB national officer, added: “Asda workers are making history.

“The result of this hearing will call time on the retailers undervaluing their predominantly women shop floor workers. 

“The entire retail sector has been built on the structural undervaluing of women's work - but GMB members are changing this.

“When the court finds shop floor work is of equal value to warehouse work it will be time for ASDA’s owners to get round the table and begin settlement talks to resolve the sex discrimination in ASDA’s pay structure.”

Asda is majority-owned by private equity firm TDR Capital, with Mohsin Issa owning a 22.5 per cent stake.

TDR Capital became majority owner after Zuber Issa sold his 22.5 per cent stake in the supermarket in June.