A legal firm has signed up hundreds of checkout staff at Asda for a mass action that could have significant implications for what constitutes equal pay.
Leigh Day has already taken on hundreds of individuals in a case that centres on the question of whether or not these customer-facing roles are of equal value to warehouse work for the company.
The firm is alleging that Asda has breached the Equal Pay Act 1970 because those on checkouts - who are mostly female - are paid up to £4 an hour less than those working in the warehouses, who are mostly male.
Discrimination and employment law expert at Leigh Day Michael Newman told the Guardian: "In the supermarkets, the checkout staff and shelf-stackers are mostly women. The people in the warehouses are pretty much all men.
"And, as a whole, the group that is mostly men gets paid more."
The waters are slightly muddied by the fact that some of the checkout operators involved in the claim are actually male, with this group hoping to gain a pay raise if the case against Asda succeeds.
According to Leigh Day, the situation at Asda is analogous to the 1968 Ford dispute, when female sewing staff downed tools after being told their work was of less value to the manufacturer - and therefore should be paid less - than that of the production line workers, who were almost all men.
The case will be fought vigorously by Asda. A spokesman for the retailer said: "A firm of no win, no fee lawyers are hoping to challenge our award-winning reputation as an equal opportunities employer.
"We do not discriminate and are very proud of our record in this area which, if it comes to it, we will robustly defend."
One notable employer to lose a discrimination case of this kind is Birmingham City Council, Britain's largest local authority.
It lost a case brought by 170 care workers in 2012, opening the floodgates for thousands more claims, which it revealed would cost around £1 billion to settle.