There were 10,538 patients, including 273 children, waiting without a bed in Irish hospitals in October, according to the Irish Nurses and Midwives Organisation (INMO).
University Hospital Limerick was the most overcrowded hospital during the month with a total of 2,043 people on trolleys.
The other four most overcrowded were Cork University Hospital with 1,034, Sligo University Hospital with 730, University Hospital Galway with 662 and Dublin's Mater University Hospital with 609 people on trolleys.
Speaking about the figures, INMO general secretary Phil Ní Sheaghda said: “We are once again seeing an unacceptable amount of patients on trolleys the day after a bank holiday.
"Over the three days of the weekend an additional 166 patients were admitted to hospital without beds.
"The system needs to get a grip on the out of control levels of overcrowding that occur following public holidays.
“The fact that over ten thousand people went without hospital beds in the month of October is concerning. There is acute pressure along the western seaboard."
She said while it is known there is less staff to deal with the growing demand on the health system, it has a knock on impact on both patient and staff safety.
Unsafe staffing levels are going to be a feature of the winter unless "we see targeted recruitment and retention plans in each hospital and community care area to allow for more nurses and midwives to be recruited at the pace in which we need them.
“Again this winter, our members are not assured that their safety and that of their patients is a priority. The HSE and Government must outline what steps are being taken both at national and local level to dramatically reduce the number of patients on trolleys," she said.
