The INMO has said it has serious patient safety concerns over St Raphael's centre for people with disabilities in Celbridge, Co Kildare.
The Irish Nurses and Midwives Organisation claims St Raphael's has inadequate staffing levels and an inappropriate skill-mix.
Nurses are calling for an urgent meeting with management of the unit to discuss the issues.
Industrial Relations Officer with the union Derek Reilly said: "There are not enough nurses on duty (and) we're saying people have to be trained properly.
"We have concerns the care is quite institutionalised…We see staff being moved from unit to unit (and) line managers being changed every number of weeks and a general disharmony within the service."