Nursing unions are claiming that agencies are paying nurses and midwives 20% above the public sector rate for the same work.
The Irish Nurses and Midwives Organisation (INMO) claims it is further evidence that public sector pay in nursing and midwifery is below the real market rate.
According to the INMO, Xtra Nursing Agency, which offers agency staff to the HSE, now pays an hourly rate at least 20% higher than that of the public sector.
Nurses in their first five years of employment are also bumped up to the fifth increment.
For a newly qualified nurse, this would mean the annual equivalent of an extra €13,000 per annum (a 46% pay difference).
For a senior staff nurse, it would mean close to €10,000 extra (20%).
INMO General Secretary Phil Ní Sheaghdha says it is also driving difficulties for recruiting and retaining staff.
"94% of nurses and midwives rejected the government’s proposals – and the market clearly agrees with them," said Ms Ní Sheaghdha.
"It’s time to face facts. Our public health service cannot hire enough nurses and midwives on these wages. They’re simply not paying the market rate.
"Until the government meet with us directly to negotiate realistic pay rates, our health service will continue to be understaffed and waiting lists will only grow longer."