The INMO claims the health service is under excessive demand coupled with inadequate bed capacity.
New figures from the Irish Nurses and Midwives Organisation show over 540 people waiting on trolleys at hospitals across the country today.
The nursing body says the situation is further compounded by acute hospital bed closures.
The organisation is calling on the HSE to introduce an emergency nurse staffing initiative to address the matter.
INMO General Secretary Liam Doran said: "At the moment the health service is under excessive demand and has inadequate bed capacity anyway.
"That's been compounded now by and inability to recruit and retain the necessary numbers of nurses."