Sinn Féin says doctors and nurses at the Rotunda shouldn't have to give up their free time to try and raise funds for equipment.
Staff have raised over €40,000 to help pay for a new heart ultrasound machine for the neonatal unit.
They say there's no government funding available for a new one - and the current machine is nearly at the end of its life.
Sinn Féin health spokesperson Louise O'Reilly says health service management should be ready for when these machines need to be retired.
"There seems to be a bottomless pit of money available for the Children's Hospital while at the same time, a few miles across town, they can't get €75,000 for a vital piece of equipment for sick, premature babies.
"I think we should have our doctors and nurses enjoying their free time off not having to volunteer in their spare time just to keep the hospital afloat."
The Rotunda Hospital is the country's busiest maternity hospital with more than 1,200 babies undergoing care at its Neonatal Intensive Care Unit every year.
Professor Afif El-Khuffash, a consultant neonatologist at the hospital, set up the GoFundMe page along with other members of staff.
He said: "We are seeking your help as our clinical echocardiography machine has reached the end of its life and the information it can give us is very limited.
"As Government funding is not available for a replacement echocardiography machine, we need help from the public to raise essential funds to purchase a new machine so that we can continue to provide the best possible care for all our babies."