The Psychiatric Nurses Association (PNA) has announced it will hold three additional days of strike action in the coming weeks.
The three days of consecutive industrial action are scheduled for February 19, 20 and 21.
6,000 union members will also strike for three days next week at the same time as nurses and midwives from the INMO.
The INMO will also stage further strikes on Febrarury 19 and 21.
The action by the PNA is part of its campaign to demand proposals to address the recruitment and retention of psychiatric nurses.
Peter Hughes, the General Secretary of the PNA, said the decision on further strike days "shows the deep frustration of nurses at the lack of resolve and urgency by the Government to bring forward realistic proposals that acknowledge the extent of the recruitment and retention crisis in nursing".
The union was not present in the Labour Court today for talks aimed at averting next week’s strike action by nurses.