The Jack and Jill Foundation has said it has grave concerns over the location of the new National Children's Hospital.
The charity - which cares for some of the country's sickest children - says the site of St James' in Dublin city centre is entirely inappropriate.
After over 20 years of work on the project, its latest incarnation is facing increased objections.
Jack and Jill CEO Jonathon Irwin will speak at a conference of the National Association of GPs this afternoon from 1.45pm. Mr Irwin is urging doctors to speak out against the planned location.
He said: "While we have no problem whatsoever with the design of the hospital building itself, we are desperately concerned by the location at St James'," he said.
"We think it is endangering sick children - particularly Jack and jill's sick children - coming in from the country."