The Irish Nurses and Midwives Organisation says there are 1,947 beds closed in the public health service, which is contributing to record overcrowding levels in the hospital system.
A review of overcrowding in the last five years by the organisation has found that last month saw the highest ever levels of overcrowding in emergency departments.
In August, 6,624 people were on trolleys awaiting a bed following a decision to admit, which was an increase of 35% on the same period last year.
It is the highest number recorded in the month of August since records began.
Overcrowding levels are up 106% since 2007, according to INMO figures.
There are around 12,000 acute beds in the public hospital system.
At any one time, beds are closed for cost-containment, infection control and other factors.
INMO General Secretary Liam Doran said the volume of acute bed closures, the reduction in long-term care beds and cutbacks in community services are having a devastating impact on the quality of care available to patients.
He said overcrowding cannot be solved by hiding the problem with extra beds on wards.
The INMO recorded 401 people on trolleys in emergency departments at the end of last month.
Based on the HSE's own performance system, five out of six main Dublin hospitals are ranked as unsatisfactory in terms of the performance of their emergency departments.
The best performing hospital is St James's, where just over 10% of patients had to wait six to 12 hours for admission.
St Vincent's University Hospital in Dublin has the largest level of overcrowding today in the country, with 38 patients on trolleys in its emergency department.
Outside of Dublin, Our Lady of Lourdes Hospital in Drogheda has the next largest number of patients on trolleys, with 35 recorded today.
The HSE has said the number of beds is not the only measure of how the health system is performing.
It said the number of patients treated in hospital is up this year, compared with last year. There is also more day-case activity.
The HSE said the health system is facing an extremely challenging financial situation for the rest of the year and hospitals must stay within their agreed budgets.