The number of people waiting on trolleys in A&E units in the State reached 422 yesterday, the Irish Nurses' Organisation (INO) said.
The record overcrowding has led to the cancellation of surgery for other patients due to be admitted to hospital.
At Wexford General Hospital, where patients have been on trolleys for days, two consultants have resigned from the management team in protest over lack of action on providing more beds for the hospital. These have been promised by the Department of Health for years.
Dr Paddy McKiernan, consultant physician, and Mr Bosco O'Mahony, consultant surgeon, said that elective surgery and elective endoscopies were being cancelled on a daily basis as a result of the overcrowding, and this was "entirely unacceptable".
The hospital's A&E unit, they added, had room for four trolleys, but there were 20 to 30 patients on trolleys every day, spilling over into the medical admissions unit and the day-care unit, which could no longer function.
Some day-surgery was also cancelled at Dublin's Tallaght Hospital yesterday, where the INO claimed there were 62 patients on trolleys. However, the hospital claimed at lunchtime that the number on trolleys was half that.
Elective surgery was also cancelled at Sligo and Letterkenny general hospitals, where there were 11 and 34 patients, respectively, on trolleys. Only emergency surgery will take place at both hospitals today.
In the south-east, elective surgery has also been cancelled at South Tipperary General Hospital in Clonmel.
Mr Aidan Gleeson, an A&E consultant at Beaumont Hospital, where there were 40 patients on trolleys, said that the situation was unsafe. "At the present time, it is not safe in the department where I am working, and I am quite sure it is not safe in many departments throughout the country."
He added that some short-term initiatives would help to alleviate the situation, such as distributing the patients on A&E trolleys to wards throughout the hospital.
However, he said that this could not be done because nurses on the wards had threatened to walk out if this happened, claiming it was also unsafe.
Mr Liam Doran, of the INO,defended the nurses' stance. He said transferring beds to wards and corridors had been tried and had failed. "If we get to a situation where you hide the problem up the house, our experience of health service managements is that we will not have a long-term solution to this problem. We have to keep this problem visible."
He added that while there were no quick-fix solutions to the problem, much more could be done at hospital level. "In view of the difficulties now being experienced by patients and staff, and the absence of any response from health service management, the INO is contacting the Labour Relations Commission to ask it to convene an emergency meeting of the A&E Forum," he said.
The newly-formed Health Service Executive said that it would co-operate fully with any reconvening of the A&E forum.