The union was hoping that the ECJ would give a clear ruling that pay scales longer than five years were discriminatory and therefore unlawful, said General Secretary Paul Noon.
"But the ECJ ruling means that we will now have to take each case to individual employers. We are ready for that challenge.
"Pay scales that are sometimes 12 or 15 years long are unfair to working mothers and undermine the whole point of the Equal Pay Act and sex discrimination law."
The 52 cases come from seven civil service departments, agencies and non-departmental bodies. They all concern pay disparities and other contractual benefits between men and women working in the same grade.
Meanwhile, Prospect is now preparing to pursue the Cadman case through the UK courts for a final decision. As the union has repeatedly demonstrated in court, pay differences of up to £9,000 have existed for many years between the Manchester health and safety inspector and her male colleagues in the same grade.
Noon called on the government to act to make a reality of equal pay and to avoid a plethora of tribunal cases up and down the country. The age discrimination regulations, effective from October 1, already specify that pay differences in the same grade lasting longer than five years must be justified by employers, he pointed out.
In the Cadman case, the ECJ ruled that where an employee can provide evidence that raises ‘serious doubts’ about whether length of service is an appropriate criterion for determining pay, employers will have to objectively justify their claim that greater experience enables employees to do their job better.
"The impact of long drawn-out pay scales is clearly discriminatory and we are confident in the eventual success of our claim, not least because the ECJ has upheld the principle at the heart of our case. Now it’s up to British courts to spell out how the law should be applied. We are pleased that the Equal Opportunities Commission will continue to back this very important case for working women," said Noon.
"The Cadman case may not have been the knockout blow that my union was hoping for in the battle for equal pay, but it was an important step forward, not a step back."