Asda is facing claims from 400 female employees who are bringing equal pay test cases against the retailer.

If the climants win then they will be entitled to six years of back pay and it could open the floodgates for more cases to be brought against other supermarkets.

Michael Newman from lawyers Leigh Day, representing the female workers, said: “The implications for any supermarket are enormous. We are very confident the jobs are pretty much the same. In the warehouses they take stuff off the shelves and stick them on a lorry. In the supermarket, they take pallets off the lorry and put the stuff on shelves.”

A spokesman for Asda insisted: “We pay a fair market rate regardless of gender.”