Around 6,000 women at Glasgow City Council have won an equal pay case on the basis that they have been excluded from bonuses for years.
The Court of Session ruled that the council discriminated against women through the introduction of payment protections for male employees.
Many of the claims from the women date back to 2006. The GMB says most of the women are carers, caterers and cleaners and are some of the lowest paid council employees.
The council says it brought in a system to ensure equal pay over 10 years ago and that to make sure that male workers did not face a drop in earnings it introduced an initial three-year period of payment protection.
It says it will begin open discussions with those workers affected and their representatives on how to go forward.