More than 500 female workers have rejected an offer to settle an equal pay dispute that would have cost Edinburgh City Council £12.2m.
Unions predicted the total claims could reach £100m.
The women, including caterers, cleaners and carers, have refused to accept offers of more than £4,000 each in compensation from the council because they believe it does not match the amount they have been underpaid over the years.
More than 2,800 claims were prompted after four dinner ladies complained last year that they were receiving lower bonus payments than male colleagues.
Union representatives at Unison said the women were entitled to up to £12,500 each.
The council offered about £12.2m to stop the case reaching the courts but 511 women are still holding out for more money.
John Ross, Unison’s service conditions convener, said: “We have told the women they are not getting what they are due.”
Lawyers at Action4Equality, the legal firm representing the women, revealed that 50 new claims a week were being brought against the council.
Frank Russell, HR director at Edinburgh City Council, said: “Throughout this exercise our aim has been to address our equal pay obligations and to make sure everyone with a valid claim has a fair settlement.”
“We have indicated to the trades unions that we are willing to discuss claims from other staff members in job areas not so far identified. However, we believe that there can be very few, if any, valid claims outstanding, and for people to start plucking figures out of the air and raising unrealistic expectations is neither helpful nor responsible.”
Crisis talks are set to take place between workers, the council and the union throughout this month, but Unison is encouraging staff to hold out for more money than the average £4,248 on offer.