Nurses working in Emergency Departments throughout the country are to be balloted for industrial action, up to and including the withdrawal of labour.
It comes as the MidWest's Emergency Department is one of the busiest in the country today.
The INMO says its members are frustrated at what they call "persistant" and "deepening" levels of overcrowding in ED's throughout Ireland.
At a meeting today, the organisations' Executive Council has decided to commence a nationwide ballot for industrial action up to and including the withdrawal of labour.
The organisation says the levels of overcrowding and understaffing is posing significant risks for the health and safety of nurses working in Emergency Departments
It comes as nurses at University Hospital Limerick report high overcrowding once more today.
Daily statistics show 30 patients on trolleys in the hospital's emergency department, along with a further 16 who are being accomodated in other overflow areas.
Hospital management have been hopeful that the opening of facilities in the Leben building this week, and the re-opening of a refurbished ward later this month, will help ease pressures there.