There are 679 patients waiting on trolleys in Irish hospitals today, the highest figure of the year so far.
The INMO's Trolley Watch figures found that 481 patients are waiting for beds in the emergency department with 198 waiting in wards elsewhere.
The figure is the second-highest ever recorded.
The worst-affected hospitals include:
Phil Ní Sheaghdha, INMO General Secretary, said the numbers were "simply obscene".
"Winter has not even started, and Irish hospitals are overwhelmed. Our members are faced with an inhumane working environment, while patients are put at ever-increasing risk.
"50,000 people marched to support nurses and midwives during the strike. They did so for an end to short staffing and a better health service.
"The government’s delay in implementing the strike settlement, along with the recruitment freeze, has driven more nurses and midwives out of the public health service.
"It’s time for extra emergency staffing, an end to the recruitment ban, and for hospitals to curtail services until safe patient and staff levels are reached."
The INMO highlighted South Tipperary General as a hospital in crisis.
They say that despite it being one of the country’s smaller hospitals, it has more patients on trolleys than some of the largest.
The 679 patients waiting on trolleys is up on yesterday's figure which stood at 595.
Last week, the INMO stated that last month was the worst-ever October for overcrowding and the second-worst month since records began.
They warned that due to the overcrowding and "chronic understaffing" patients are at "grave risk".