GMB union says the mostly female shop staff are on ‘cusp of justice’ with claim that could cost supermarket £1.2bn. Thousands of Asda workers have won the latest stage in a decade-long equal pay case against the supermarket that could lead to a payout worth £1.2bn. The GMB union said the workers were on “the cusp of justice” after Manchester employment tribunal ruled that 12 out of 14 lead claimants in the case, which involves 60,000 mostly women working shop-based jobs, had roles that were of equal value to their mostly male counterparts employed in the retailer’s warehouses.

The case, which is backed by the GMB and the law firm Leigh Day, centres on the fact that the mostly female shop workers are paid up to £3.74 an hour less than the predominantly male warehouse staff. The long-running court battle has implications for workers in all the big supermarkets who are involved in similar cases. The total industry bill for compensation in back pay could be as much as £8bn.

The ruling found that checkout operators and shop floor assistants in categories including bakery, chilled, produce, customer services and the George clothing departments all carried out work of equal value to at least one warehouse role. Two roles were found not to be of equal value – online shopping packers and store workers who only handle packaged or tinned groceries. Those positions are understood to equate to about 11,000 claimants – or a fifth of the total. The GMB said it was considering an appeal on their behalf.

Nadine Houghton, a national officer for the GMB, called on Asda, which is struggling to turn around falling sales after a private equity-led takeover, to “stop wasting time and money dragging this case through the courts and get round the table with us to agree a settlement”. “This is a historic step towards securing equal pay justice for tens of thousands of Asda workers, but it is tainted with bitter disappointment for those who now face an appeal,” she said.

The women, who launched their claim in 2014, now face just one final stage in the case, which requires Asda to provide a reason, not related to sex, for the difference in pay. Sign up to Business Today. Get set for the working day – we'll point you to all the business news and analysis you need every morning. after newsletter promotion. An Asda spokesperson said: “We strongly reject any claim that Asda’s pay rates are discriminatory. Asda will continue to defend these claims at the next stage of the litigation because retail and distribution are two different industry sectors that have their own market rates and distinct pay structures.”.