The head of the INMO, Liam Doran, has described the midwife to patient ratio at Portlaoise Hospital as "immoral".
Reports today suggest that in January, Portlaoise Maternity unit had only one midwife for 70 births, compared to the internationally recommended ratio of one to 29.5.
The Irish Nurses and Midwives Organisation says the low level of nurses is affecting patient safety and leading to death in some cases.
General Secretary of the INMO Liam Doran said: "You'd certainly be depressed, I certainly think it's immoral. The figures released in March confirm that Ireland, in terms of midwifery staffing had an average of about 1:40, the internationally accepted ratio is one midwife to 29.5.
"You'd have to ask, are mothers in Ireland, newborns in Ireland, are they not entitled to the same quality of care?"
The Midwestern Regional Hospital in Portlaoise is currently under investigation after the deaths of five babies there in seven years.
Liam Doran says it is time for action.
He said: "There is no unit in this country that reaches the international benchmark of best practice and that is a shocking indictment.
"So we need less reports about these things, we need action on these reports, and some of that action has got to be additional midwifery staff now."
The issue of patient safety as a result of overloaded staff is one of the focal points of the annual conference of the Irish Nurses and Midwives Organisation starting in Kilkenny this afternoon, under the banner of "safe staffing, safe care, safe patients".
President of the INMO Claire Mahon says understaffing can have dire consequences.
She said: "By having fewer nurses and midwives on the wards, patient care is comprimised up to and including death."
The conference begins this afternoon.