Members of SIPTU who are employed by the HSE as Health Care Assistants (HCAs) in Home Support, in the northwest, mid-west and south regions have begun a ballot for industrial action, up to and including strike action.
The union has accused the Health Service Executive of failing to implement national agreements concerning their terms and conditions of employment.
SIPTU said the ballot follows years of unresolved issues relating to pay, rostering and working conditions, despite multiple agreements being reached on these issues under the auspices of the Workplace Relations Commission (WRC).
"Among the issues in dispute are underpayments for hours worked, dating as far back as 2018," said SIPTU Organiser Graham Macken.
"Rostering principles agreed between SIPTU and the HSE in 2018 have not been implemented in full in some areas, resulting in breaches of the Organisation of Working Time Act," Mr Macken said.
"Our members have reported suffering from burnout due to working up to 12 days in a row, being rostered for excessive split shifts and not receiving appropriate breaks," he said.
SIPTU said it has also been engaging with the HSE regarding the continued use of contractors, which it believes is inconsistent with their commitments under public service agreements and previous WRC agreements.
The HSE has been contacted for comment.