Legal action to secure equal pay for women in the public sector is being launched by Wales’ largest trade union.
Unison, which represents more than 95,000 members in Wales, 65% of them female, said its campaign was on behalf of thousands of underpaid women.
It said local councils had not stuck to the April 2007 deadline of a three-year deal agreed to end pay discrimination.
Councils have said they are committed to equal pay but have warned of the financial effect on their services.
The union said it has been left with “no alternative” to mass litigation.
The deal, made in April 2004, had seen councils commit to negotiating new equal pay salary structures.