Before the UK left the EU, the CJEU was asked whether part of European law could be relied upon by people in the UK making equal value claims against their employer.

Under EU law, a woman can compare her role to that of a man’s working in a different establishment if a ‘single source’ has the power to correct the difference in pay.

The CJEU said in its judgment: “Where such pay conditions can be attributed to a single source, the work and the pay of those workers can be compared, even if they work in different establishments.”

Leigh Day represented more than 50,000 supermarket shop floor workers, most of whom were women, who claimed they were paid unfairly in comparison to distribution centre colleagues, most of whom were men.

Earlier in the year, the Supreme Court ruled that Asda shop floor workers could compare their roles to those of their colleagues in distribution centres for the purposes of equal pay.

Despite this decision, other supermarkets are still arguing that the roles are not comparable.

Kiran Daurka, a partner in the employment team at Leigh Day, 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.

“Clarification from the CJEU confirms that this single source test can be relied upon by people in the UK bringing an equal value claim. This means that employers can no longer hide behind the grey areas of UK law. It’s time for supermarkets to accept that the roles of shop floor workers and distribution centre workers are comparable.”

Pam Jenkins, who works at Tesco, said: “To get a judgment confirming shop floor workers can use an easier legal test to compare their jobs to male colleagues in distribution is up lifting.

“I’ve always been proud to work at Tesco but knowing that male colleagues working in distribution centres are being paid more is demoralising.

“I’m hopeful that Tesco will recognise the contribution shop floor workers make to the business and reflect that in our pay.”