The record number of hospital patients on trolleys is a warning to the government to take corrective action to solve the problem.
Figures for last month from the INMO found 11 thousand 856 patients were left on trolleys, including 300 children.
The numbers were higher than January which saw the worst levels of daily hospital overcrowding since the INMO began counting trolleys.
Cork University Hospital was the second most overcrowded hospital in the country last month.
The union's General Secretary, Phil Ní Sheaghdha is expecting chaotic scenes after the bank holiday.
"On the Tuesday post bank holiday, or the first working day post bank holiday, the figures are double what they were the previous week on the last working day.
"We know that's something is happening around these weekends.
"There's a backup, and a reduction in the discharge numbers, which means that there aren't as many beds available."
