More than a million workers are to be balloted for strike action over planned changes to their pensions.
Nine trade unions will begin the process in the coming weeks unless the government drops plans to alter the local government scheme.
Town hall workers, some teachers, probation officers and other public sector workers will be involved.
The unions said the move was in protest at planned cuts to the pension scheme.
Dave Prentis, general secretary of the public sector union Unison, warned government and council employers the dispute was serious and the “clock was ticking”.