Members of the Fórsa trade union working in clerical and administrative roles in the Health Service Executive have voted for industrial action.
It follows a decision by the HSE last month to halt all recruitment of clerical and administrative staff.
Fórsa's National Secretary for Health and Welfare has said there are a number of reasons why staff have decided to engage in a work-to-rule.
Speaking on RTÉ's Morning Ireland, Ashley Connelly said members have voted for industrial action after a prolonged process of engagement with their employer in relation to the overreliance of agency staff and the extended and excessive use of private external consultants.
She said the "final blow" for members was when the HSE put a recruitment pause in place, which means no positions can be filled in clerical administration or managerial grades without the sanction of a national director.
"These are the only group and category in the HSE that has been subject to this unilateral decision, no other grade or category," she said.
Ms Connelly said members want to have a limited impact on service users or on patients, so they have taken the decision to engage in a work-to-rule, which will have an impact on the corporate levels within the HSE and the Section 38 agencies.
"This was something they thought about and have decided at the commencement of this industrial action that they will limit the impact on service users and patients," Ms Connelly said.
She said that where an employer chooses not to fill a vacant post, Fórsa will be instructing its members not to carry out the duties attached to that post.
Ms Connelly warned that use of agency workers and the excessive use of private external consultants is three to four times more expensive.
The HSE needs to engage with Fórsa to find solutions and rushing to the private market is having a negative impact on HSE budgetary overruns, Ms Connelly said.
"The clerical admin working in the health services are always scapegoated. They're too easy of a target and they are fed up and angry at their employer for yet again solely targeting them," she said.
Speaking on the same programme, the HSE's Chief Clinical Officer Dr Colm Henry said he noted that the union had voted for industrial action.
He added: "That will now enter an industrial relations process. Obviously, our hope is that process will not lead to industrial action. Let it go through that process and see what happen."
