SIPTU has called on the Government to extend the terms of the public sector pay deal to workers in the community sector and Section 39 organisations.
It comes ahead of a series of strikes next week at agencies in counties Cork, Kerry, Galway, Mayo and Donegal.
The organisations impacted include Enable Ireland, the Irish Wheelchair Association in Cork, St Josephs Foundation, EmployAbility Cork, Western Care, Ability West and selected community employment schemes in Donegal.
The action is being taken as part of a campaign demanding better pay for the community and voluntary sector.
Unions say that health and social care professionals employed in agencies funded by the Health Service Executive are paid significantly less than equivalent workers employed directly by the HSE and other state bodies.
'Section 39' organisations are contracted to provide services on behalf of the HSE for a funding grant in accordance with Section 39 of the Health Act 2004.
The Department of Health says that because such organisations are privately owned, setting pay rates for their staff is not a matter for the Government.
SIPTU has accused the Government of adopting a "pass the parcel" approach with no department willing to address the concerns of community workers.
"They have been left in the dire situation of being on the same rate of pay since 2008 with no way of securing a rise, apart from taking the campaign of industrial action on which they have now embarked," said SIPTU Public Administration and Community Division Organiser Adrian Kane.
"We are calling on the Government to engage with the workers' unions and discuss how we return to a system of linking these vital workers’ pay to movements within public service pay," he added.
