A large multiple equal pay claim can be one of the most complex, costly and reputationally damaging employment disputes that employers can face. Of the three basic types of equal pay claim, the most factually complex are multiple 'equal value' claims. These are usually based on claimants identifying a 'comparator' of the opposite sex, who is doing work of equal value to the claimants but who is paid more. If the claims succeed, an employment tribunal can award compensation equivalent to the pay discrepancy over a period of six years prior to the date of the claim, and the employer must equalise pay between the successful claimants and their comparators for the future. An employer who is presented with large numbers of these claims is often facing very considerable financial risk.

All of the above helps to explain why an employment tribunal preliminary hearing in June this year, in a multiple equal value claim against Asda, involved no fewer than six barristers, including three QCs. The essential issue for the tribunal was whether the female claimants (who were employed in Asda's retail stores) were permitted to rely on male comparators who worked in distribution depots. At first sight one might think that this is a no-brainer – if the claimants and comparators were all employed by Asda, why wouldn't they be valid comparators? Asda argued that they were not, for three main reasons: first, the distribution staff worked in different 'establishments' from the retail staff; second, they were on different terms and conditions; and third, those terms and conditions were negotiated separately from the retail staff conditions because the distribution and retail operations within Asda were separately managed – in equal pay terms, there was no 'single source' of terms and conditions for the claimants and comparators.

The tribunal has now released its decision and has rejected these arguments: although the male comparators did work in different establishments and in a different operational function to the claimants, in summary the tribunal found that there were common terms and conditions applying to both, and that the Executive Board of Asda was the 'single source' of those terms and conditions: it could have introduced equality between the claimants and comparators. The claimants could therefore rely on men employed in the distribution depots as equal value comparators.

Some of the legal issues in this case are difficult and potentially far-reaching in equal pay law and, given the potential value of these claims, it seems highly likely that they will be revisited on appeal. Watch this space.

Brierley and ors v Asda Stores Ltd