Morrisons is contending with further equal pay claims from “thousands” of current and former female workers, who say that they have been underpaid.
The supermarket is already battling similar claims from in-store colleagues, who believe they should be paid the same as warehouse staff, which could leave it with a £1bn backpay bill.
Law firm Roscoe Reed, which is representing the claimants, says that the claim involves not just base level salaries but bonuses, holidays and sick leave.
The firm said that the women could receive average backpay of £15,000 but the grocer said it believed that the number of claimants was much smaller and added that it would be contesting the case.
Other members of the big four are also facing similar cases, which have all been brought by law firm Leigh Day, which brought the initial Morrisons case.
Roscoe Reid lawyer Ellie Pinnells said: “There is a clear case that female roles have been underpaid for a long time and employees are very likely to win their equal pay cases.”
“Asda has tried to fight every point, but has had a string of defeats in the court. Let’s hope Morrisons takes a different approach and tries to put an end to decade-long unfair pay on their shop floors.”
However, a Morrisons spokeswoman said: “We are perplexed that this law firm is talking about ‘thousands’ of claimants as they have written to us recently with a significantly smaller list of claimants.
“We believe we pay our colleagues fairly and equally for the job that they do, irrespective of their gender, and we will be defending this claim.”