Nine times as many people were on waiting on trolleys in Irish hospitals last month than during April of this year, according to the Irish Nurses and Midwives Organisation (INMO).
According to INMO figures, the total number of people without hospital beds rose to 4,499 in October, from a low of 497 this past April.
The worst affected hospital in the country was University Hospital Limerick (UHL), which had 1,064 people waiting on a trolley last month.
Cork University Hospital saw the second-highest October total, with 685.
The INMO says that trolley counts have been compounded by the impact of high numbers of healthcare workers testing positive for Covid-19.
The Health Protection Surveillance Centre (HPSC) reported earlier this year that over 32% of Covid-19 infections were among nurses, and the IMO is now calling for plans to combat overcrowding in Irish hospitals.
This, the INMO says, would allow for increased staffing in the context of high numbers of healthcare worker infections.
The INMO says the rising numbers of people without hospital beds are very concerning, particularly as the winter season begins.
INMO general secretary Phil Ni Sheaghdha said: "We were told at the beginning of this pandemic that there would be a zero-tolerance policy toward overcrowding across the health service, to ensure hospitals were safe.
"Unfortunately, we’re now seeing an average of 200 patients per day without beds, and the figures are climbing.
“This is highly dangerous at the best of times, but this year we simply cannot afford to accept this level of risk, for patients or for staff. We are over a month into the winter period and we’re seeing 4,500 patients per month on trolleys.
The INMO also stated they are in currently discussions at the Workplace Relations Commission regarding vacancies that must be filled within the UHL group, if plans to increase bed capacity there are to go ahead.