The Irish Nurses and Midwives Organistaion has said there are 81 patients on trolleys at University Hospital Limerick waiting admission to a hospital bed, which it said is the highest daily figure recorded in an Irish hospital.
Overall, there were 594 patients on trolleys in emergency departments or on wards in hospitals around the country this morning, with Cork University Hospital also badly affected where 50 patients were waiting.
In a statement, CUH said it had lifted a HSE-status black escalation level - meaning the hospital is in a "critical position and clinically unsafe" - at 8am after 70 patients were recorded on trolleys by the INMO yesterday.
CUH management says the number of patients on trolleys in the emergency department was 23 as of 12pm today, down from an earlier figure of 31 compiled under the hospital's own count.
A consultant in emergency medicine at CUH, Dr Conor Deasy, described the situation yesterday as the worst he had seen, with ambulances queuing for hours at one point as there was no way to offload patients safely.
There are 43 patients on trolleys at University Hospital Galway today, according to the INMO.
The INMO Industrial Relations Officer in Limerick said staff and patients at UHL are under intolerable pressure.
Mary Fogarty said the overcrowding comes less than a week after a 17-bed ward at the hospital was shut and she called on the Minister for Health to intervene "as an urgent matter of patient and staff safety".
Speaking on RTÉ's News at One, Ms Fogarty said: "I've been to the emergency department this morning and all around the wards and I can tell you our figures are accurate.
"All of those patients, we could see them visibly on trolleys and it is causing significant levels of distress for the patients and for the nursing staff seeking to care for those patients."
Ms Fogarty added that she has also written to the Minister Simon Harris requesting that the ward that was closed last Friday is immediately reopened.
She said the union had asked the HSE not to close the ward "until such time as they had put in place alternative measures to address the overcrowding.
"This is the most overcrowded hospital in the country, it regularly runs at 50 up to 70 patients on trolleys and we knew once this ward closed they had no alternative area to put these patients."
The Chief Clinical Director of the UL Hospital Group said there had been no reduction in bed capacity at UHL.
Professor Paul Burke said the bed complement at the hospital was increased by five or six over the period the union was speaking about.
Prof Burke also rejected claims that fire escapes were blocked at the hospital this morning.
He said there were three trolleys on wards early this morning, with a maximum number of 29 trolleys on the wards.
"It is not a crisis, it is something we deal with all the time and we have to deal with," he said.
He urged members of the public to attend "our medical assessment units or the local injury units in our other three hospitals, our small model two hospitals" if possible, instead of coming to the emergency department.