Nurses at St James's Hospital in Dublin say they are against having to pay for their parking, because of security fears.
Staff have received a memo, telling them they'll have to pay up to €500 a year for a space in the hospital campus, which is also the site of the new National Children's Hospital.
Siptu is planning to ballot its members at the hospital on possible strike action over the move.
Jonathan Irwin of the Jack and Jill Foundation says this would not arise if the new children's hospital had been situated in Blanchardstown.
He says staff are worried about their personal security if they have to park a distance away or use alternative transport.
Mr Irwin said: "There have been too many incidences where nurses have been attacked. They are just not going to do it.
"The Government is trying to attract nurses back to this country, but what paediatric nurse will come to St James' with its security problems, with its access problems?
"It has so many problems, none of which would exist if they had decided to build the hospital beside the new Rotunda at Blanchardstown."