The HSE spent over €1.1 billion on agency staff in less than two years.
According to Freedom of Information figures released to Newstalk, almost one-quarter was spent on nurses.
The HSE spent €568 million on agency staff in 2021, and €543 million in the first 11 months of last year.
Across the 23 months, almost €240 million was spent on nursing staff, €200 million on management and administrative staff, and over €101 million on paramedics.
Beaumont Hospital consultant Bill Tormey said knocking the health service is not helping anyone.
"Why do the Irish graduates not want to stay in their own country?
"I am delighted to work in Ireland; and everybody knocking the place right, left and centre is doing nobody's morale any good.
"It doesn't do anybody any good to have every hospital and every nursing home and every acute service slagged off on an industrial scale all the time", he added.
The HSE has said the availability of health staff continues to be a challenge, not only in Ireland but around the world.
Where there are shortfalls, agency staff are employed.
The HSE said in a number of instances in recent times, it has been unable to fill a vacancy even with agency staff.