Independent analysis by employment lawyers, Thrive Law, found that the latest ruling does not mean that all shop workers should expect a pay rise.
On Thursday, The European Union Court of Justice (ECJ) ruled that EU rules guaranteeing equal pay for male and female workers can be invoked in a dispute over pay for thousands of Tesco workers, in a blow for the supermarket giant.
The bloc’s top court indicated that pay conditions for shop floor workers can be compared with the company’s distribution staff.
However, Thrive Law's managing partner, Jodie Hill, warned that Asda and Morrisons workers should not get their hopes up over compensation and said a decision may take years as the various battles proceed through the courts.
Ms Hill said: "This ruling by the ECJ is a victory for women working at Tesco as it confirms that staff can now compare themselves to colleagues if there is a single body responsible for equality. This decision will provide some much-needed clarity in this area of law.
"This does not mean that all shop workers should expect a pay rise though. There are still more hearings on the claim, and there are also similar equal pay claims against Sainsbury’s,
Morrisons and Co-op. The supermarkets continue to argue that the roles are substantially different, and this explains the variation in pay.
"This follows a matter against Asda earlier, where it was confirmed that shop workers can compare their roles with those of their colleagues in distribution centres for the purposes of equal pay.
"This decision will now bind the UK courts, despite us leaving the EU."
Ms Hill said an equal pay claim works out whether employees should receive equal pay for work of equal value.
She added: "However, the comparison centered around whether the shop workers (the majority of whom are female) should be paid the same amount as the distribution centre workers (mostly male), on the basis that the same 'single source' had the power to correct the difference in pay.
"The laws around equal pay are complex and have been subject to a great deal of litigation. Until now, it has been unclear whether employees could rely on EU law to support claims that they should receive equal pay for work of equal value, even where the comparator would appear to carry out a very different role."
On Thursday, the ECJ said the legal test for comparability is one of three tests involved in the Tesco case, which could take years to conclude.
A Tesco spokesperson said: “The jobs in our stores and distribution centres are different.
“These roles require different skills and demands which lead to variations in pay – but this has absolutely nothing to do with gender.
“We reward our colleagues fairly for the jobs they do and work hard to ensure that the pay and benefits we offer are fair, competitive and sustainable.
“These claims are extremely complex and will take many years to reach a conclusion. We continue to strongly defend these claims.”
Law firm Leigh Day represents more than 50,000 supermarket shop floor workers, most of whom are women, who claim they are paid unfairly in comparison with distribution centre colleagues, most of whom are men.
Kiran Daurka, a partner at the firm, said: “This judgment reinforces the Supreme Court’s ruling that the roles of shop-floor workers can be compared to those of their colleagues in distribution centres for the purposes of equal pay.
“For a long time, employers have argued that UK law in this area is unclear, but this judgment is simple: if there is a single body responsible for ensuring equality, the roles are comparable."
A spokesperson for Leigh Day told The Yorkshire Post: "It won’t impact Asda because they have already moved on from the comparability stage to equal value, but our legal teams will be asking Co-op, Morrisons and Sainsbury’s to concede on the issue of comparability."
The Supreme Court decided in March that Asda store and depot roles could be compared for the purposes of Equal Value, which means Asda is already a step on from the Tesco ruling.
However, this is just one stage of a very complex process and the issue of whether the roles are of equal value still has to be determined. If they are found to be of equal value, the final stage would consider whether there are any material factors that determine pay differentials, for example, geography.
Lawyers said the various court cases are extremely complicated and could take years to conclude.