The Irish Nurses and Midwives Organisation recorded over 9,700 patients who were admitted to hospital without a bed in August.
That's a record-breaking recording of numbers for the month.
University Hospital Limerick was the worst affected by overcrowding, with 1885 patients waiting for a bed.
That's followed by Cork University Hospital at 984 patients and University Hospital Galway at 920.
The INMO says the previous August record was last year, and the following winter was 'beyond what could have been imagined'.
As a result of the rise in pressure on hospital staff and the increase in the number of patients on trolleys, they are now warning of a difficult and dangerous winter in hospitals this year.
Health spokesperson for the Labour Party, Duncan Smith, says the issue is very concerning.
"We are absorbing crisis levels of waiting lists in our health service all year round when we know that particular time of year that is through the winter, there will always be a spike in the pressures put on our hospitals. So to see the numbers throughout the summer and these record levels for August is a cause for huge concern".
"It is very clear that we are living through, on a month-by-month basis, a crisis in our health service and when it comes to the winter, we are going to see that crisis increase. I agree with the HSE CEO that we don't need a winter plan, we need an all-year plan, but we need to see that plan and we need to see that plan being implemented and being successful, and so far we're not seeing that".
