The Irish Nurses and Midwives Organisation says last month saw a 40% increase in the number of patients on trolleys in hospitals when compared to August 2014.
The INMO says in total there were 6,518 admitted patients left on trolleys last month.
It said that overcrowding in Irish hospitals has increased every month so far this year when compared to last year.
The hospitals with the greatest levels of overcrowding during August, according to the INMO, were: Drogheda (680), Beaumont (678), Limerick (618), UHG (458), CUH (399) and Tallaght (395).
The group said that this is a "very disturbing trend" and repeated its demand for a meeting of the High Level Implementation Group to solve the issue.
Speaking this morning INMO General Secretary Liam Doran said: "This is the14th month in a row when, year on year, the level of overcrowding has deepened with patient care compromised, on a daily basis, as a result.
"We are now beginning the early autumn/winter period, which will only see, in the absence of emergency measures, the overcrowding situation worsen still further as demand continues to grow against the background of staff and bed shortages.
"The government must accept the request for additional funding made recently by the HSE.
"The additional resources being sought are required to allow the health service meet existing demand in a quality assured and patient sensitive manner."