Almost 10,000 patients were on trolleys in August.
The INMO is warning of a difficult winter in hospitals following the publication of its August 2023 trolley figures.
It shows it has been the worst August for hospital overcrowding since the INMO began counting trolleys, with over 9,720 patients admitted to hospital without a bed.
The number of children on trolleys is escalating at a worrying rate, it said, with over 167 children admitted to hospital without a bed throughout the month of August.
The most overcrowded hospitals in the country this month again include:
University Hospital Limerick 1,885
Cork University Hospital 984
University Hospital Galway 920
Sligo University Hospital 737
Letterkenny University Hospital 539
Naas Resident and INMO General Secretary Phil Ní Sheaghdha said: “There’s no doubt this winter is going to continue the pattern of difficult and dangerous times in our hospitals.
“The summer period used to see an easing off in overcrowding figures but this year numbers admitted to inappropriate spaces, trolleys and chairs have been alarmingly high too early in the season.
"The new so-called target of no more than 320 people on trolleys set by HSE was only achieved on five days this year.
“Last year was the previous record for August overcrowding, and the winter that followed was honestly beyond what we could have imagined. This August is somehow worse again, and our members are worried, for themselves, and for their patients, about what is in store for them over the coming months.
“The ongoing increase shows how urgently we need to implement safe staffing legislation, so that hospitals have sufficient staff to diagnose, treat and discharge patients safely, and vulnerable people are not languishing on trolleys and chairs for days at a time.
“Medical evidence shows that spending more than six hours on a trolley is detrimental to a patient’s long-term health outcomes. In stark terms it increases the mortality rate by over 8%.
“The INMO is of the view that this situation is not being met with the required urgency or focus required.
"The constant state of overcrowding in our hospitals is a leading cause of nurses and midwives intending to leave their current work areas and indeed the professions altogether," she added.