The Irish Nurses and Midwives Organisation (INMO) says "record numbers" of people are waiting on hospital trolleys.
Figures for Wednesday show 677 people are waiting on trolleys - an increase of 21 from Tuesday.
The INMO says Dublin hospitals, particularly St James's and Tallaght Hospitals, have had a big increase overnight with a total of 28 and 23 respectively.
It says the Midland Hospitals are all very overcrowded, particularly Mullingar and Tullamore, with figures of 38 and 42.
St. Luke's Hospital Kilkenny has a total of 54, and University Hospital Limerick is at 53.
The INMO says these remain the hospitals with the most patients on trolleys.
Our Lady of Lourdes Hospital in Drogheda has a figure of 26.
The INMO has sought an emergency meeting of the Emergency Departent Taskforce and says it is awaiting confirmation from the Health Service Executive (HSE).
INMO General-Secretary, Phil Ni Sheaghdha, said: "As predicted the January figures are unacceptably high.
"We are very concerned at the level of planning to avoid the situation that has been engaged in some locations and we have sought to meet with the HSE as a matter of urgency.
"We are awaiting their confirmation that this meeting will take place today, with a view to examining alternative arrangements for hospitals that are simply too overcrowded to continue to accept admissions.
"It is clear that a national emergency is now in place and certain locations simply cannot cope."
'This isn't a temporary blip'
The Irish Medical Organisation (IMO), meanwhile, said the current situation exposes "the perilous state of the Irish health services".
The organisation argued: "This isn’t a flu crisis or a temporary blip... this chaos is the reality of our health services today.
"We are only ever hours away from a crisis such as we are experiencing this week."
The IMO is calling for more hospital beds and investment in general practice, and highlighted the need to attract more consultants into the health system here.
In a statement this evening, Health Minister Simon Harris said he is being regularly updated by senior HSE official about the current situation.
He said: "I want to recognise again the intense efforts of all our staff across the health service and the very difficult conditions patients experience at this time of high pressure in our emergency departments.
"It is vital that we begin to see an impact from the exceptional measures being undertaken to reduce overcrowding in our EDs and tomorrow I will be directly updated by each Hospital Group CEO on this."
He added: "While recognising that there is no one-size-fits-all solution, we must continue to ensure the lessons that can be learned from those hospitals performing better are applied across the system."
Additional reporting by Stephen McNeice