The European Court of Justice (ECJ) has handed down its decision in the Cadman case, described as the most important equal pay case in a decade.

And although on the surface, mothers appear to have lost their right to equal pay, lawyers are already pointing out that the judgment won’t apply in every case.

The facts behind the case are that Bernadette Cadman, a Health and Safety Executive inspector, discovered that she was being paid up to £9,000 less than four male colleagues who were doing the same job.

The original tribunal hearing found that women were disproportionally adversely affected by pay systems based on length of service. The appeal tribunal found there was no need for justification, so the case went to the Court of Appeal which referred it to the ECJ.

Evidence from the Equal Opportunities Commission showed that women generally have shorter length of service than men, owing to maternity leave and other care duties. Therefore pay awards based on length of service are an important factor in the gender pay gap.

The advocate general’s opinion backed the original tribunal but the ECJ has stepped back from finding automatic indirect discrimination in pay awards based on length of service.

Instead, the court said that length of service is an appropriate way of attaining the “legitimate objective of rewarding experience acquired which enables the worker to perform his duties better”.

As a result, an employer does not have to justify a pay system based on length of service – in future claims it will be up to the employee to “provide evidence raising serious doubts in that regard”.

So, the case does not close off equal pay actions where women have taken maternity leave – but there is a higher hurdle for claimants to jump in order to prove discrimination.

If extra length of service will not make an employee better at their job then a pay system based on service is unlikely to be justified.

The Cadman case will now return to the UK courts and Prospect also plans to pursue other cases based on the judgment.

Emma Hawksworth, a partner in Russell Jones & Walker’s Employment Department, who represented Mrs Cadman, said: “The decision gives some much needed clarification on the law and marks a significant step forward in the move to narrow the gender pay gap.

“Additional experience does not lead to better performance indefinitely or in every case. Employers will have to ensure that their pay schemes reflect this.”