Nurses in SouthDoc have voted to take industrial action over pay parity with the public service.
SouthDoc provides an out-of-hours doctor service in Kerry and Cork for urgent medical needs.
The nurses have voted to take industrial action over what they call the failure of their employers to address a claim for parity of pay with public service employees in identical roles.
The INMO says this issue has far-reaching implications for the vital out-of-hours service.
Industrial Relations Officer with the INMO, Liam Conway, says SouthDoc nurses represented by the union are close to a 20% pay gap by the end of the current public sector agreement.
He said this is unfair, unjustifiable, and is leading to significant retention issues for this critical service.
Mr Conway added that these strong views of members in SouthDoc show the importance of reaching an agreement with their employer to avoid industrial action entering the winter months.
A similar industrial action was also approved by CareDoc nurses, which provides out-of-hours cover in the South East and North West of the country.