Supermarkets with similar workforce structure could also face legal action
More than 400 female employees at supermarket Asda, which employs 172,000 people, have brought a claim for equal pay against their employer.
The group, represented by law firm Leigh Day, said they have been underpaid in comparison to men in roles with equivalent work and skills requirements to their jobs. Their male counterparts work in the organisation’s distribution warehouses.
If the claim is successful the women could be entitled to six years back pay, their legal representatives said.
An equal pay comparison has been possible in this case because the supermarket runs its own distribution centres, employing its own staff.
Other big supermarkets that also have their own distribution centres, such as Tesco, Sainsbury's, Morrisons, Marks and Spencer and John Lewis, could face similar equal pay claims if this test case is successful.
Michael Newman, employment lawyer at Leigh Day, said: "The implications for any supermarket are enormous.
"In the supermarkets check-out staff and shelf-stackers are mostly women. The people in the warehouses are pretty much all men. And, who would be surprised, the group that is mostly men gets paid more.
"We are very confident that the jobs are pretty much the same. In the warehouses they take stuff off the shelves, put it on a pallet and stick it on a lorry. In the supermarket, they do the reverse: take the pallets off the lorry, unstack them and put stuff on the shelves,” he said.
Newman explained that there had been “huge advancements” on equal pay in the public sector, while the private sector is “still in the 1970s”.
He explained: “Job evaluations don't happen. Cases aren't brought. So you still get this very segregated workplace. Women are over here doing the women's work and men are over there doing men's work."
In a statement Asda said: "We are aware of a small number of claims. We pay a fair market rate for the job people do regardless of gender and we don't recognise discrimination in our business."
A Manchester employment tribunal is expected to hear the test case in the next two months.
In October 2012 Leigh Day won a ruling in the Supreme Court that extended the time limit for people to bring a claim of equal pay discrimination after leaving the employer from six months to six years.