There were 81 patients waiting for admission to a bed at University Hospital Limerick today, according to figures from the Irish Nurses and Midwives Organisation.
It is the joint highest number recorded at the hospital and matches levels reported on 3 April and 11 July this year by the nurses' union.
The INMO said that UHL was the most overcrowded hospital last year, when 10,000 patients were waiting for admission to a bed.
It described the overcrowding situation at the hospital today as "very unsafe".
Speaking on RTÉ's News at One, spokesperson Mary Fogarty said there were 44 patients on trolleys in the emergency department and a further 37 on wards.
She said this was making it "absolutely impossible" for the nursing staff to deliver acceptable standards of care.
Ms Fogarty said: "They don't have enough staff on the floors to cater for all the patients.
"They're in obscure areas of hospitals, lying on corridors, behind screens, in areas where they can't be properly examined. The situation is very unsafe.
"It's Illogical that you would have this situation and not curtail other services to deem it safer for the patients."
In a statement, the UL Hospitals Group said the hospital is experiencing high numbers of presentations in recent days, including many elderly patients.
It regrets that patients have experienced long wait times in the emergency department for a bed to become available and says it not the level of service it wishes to provide.
It reiterated its appeal for the public to use the Emergency Department for emergencies only, and to consider all care options before attending the emergency department.
The added: "However we want to reassure our the public that every patient in ED continues to receive expert medical care and every effort is made to make their stay as comfortable as possible."
Overall around the country, there were 534 patients waiting for admission to a hospital bed the INMO figures show.
The HSE TrolleyGar figures, which just count those in emergency departments waiting for admission to a bed, put the national figure at 386 today.
The highest level of hospital overcrowding recorded was 714 patients seen on 12 March last year.