The ruling came after several female local authority employees took their employers to court, because the women had not been offered pay protection like their male colleagues.
In the cases of Redcar and Cleveland Borough Council vs Bainbridge and others and Middlesbrough Borough Council vs Surtees and others, the claimants argued not that pay protection was wrong but that they should have had a right to benefit from it.
Rachel Crasnow, barrister at Cloisters, the law firm that represented the successful claimants, said: "The court's ruling, that discriminatory pay protection is unlawful, could pave the way for thousands of new equal pay claims against local authorities and the NHS. This would be in addition to the thousands of equal pay claims that are already in the system."
The purpose of a pay protection scheme is to provide initial period of protection if an employee takes a reduction in their earnings to help them adjust.
Discriminatory pay protection schemes deemed unlawful
Thousands of low-paid women in the public sector are set to lodge claims against their employers after a critical equal pay test case ruled that pay protection schemes discriminating in favour of men are unlawful.