The head of a major charity has been sent two anonymous letters setting out details of alleged cost overruns in the planning and design phase of the new national children's hospital, he has said.
Jonathan Irwin, chief executive of the Jack and Jill Foundation, believes the correspondence proves the St James's Hospital site, where the children's hospital is to be located, is inappropriate for the facility.
The letters set out details of an overspend, Mr Irwin said.
He has previously said the St James's site is an unsuitable location because of parking and access issues.
The children's charity boss believes land beside Connolly Hospital in Blanchardstown is the better option.
The Department of Health had not responded to Mr Irwin claim at the time of writing.
However, it reiterated earlier this week that the St James's campus is the best location for the state-of-the-art facility.
"There is no perfect site for the new children's hospital. It is widely accepted that one or more of the other sites would have advantages from the point of view of road access, cost and planning.
"But St James's is second to none when it comes to the range of medical facilities and specialist staff already on campus. No other hospital comes close," a spokesperson for the Department of Health said.
The Dolphin Group, tasked with reviewing the options, found the "St James's campus already has the widest range of specialist and medical services on site".
The spokesperson added: "None of the recent commentary brings any new information to the table. This was all considered by Dolphin and the Government at an earlier stage.
"The decision to locate the hospital at St James's is now made. The project team has been appointed.
"All things going to plan, planning permission will be secured next year and construction on the new hospital and the satellite centres in Blanchardstown and Tallaght will commence.
"The satellite centres will be seeing children within two or three years from now, and services are due to start moving over to the main hospital in subsequent years."
The hospital was originally to be located beside the Mater but those plans had to be abandoned.
But the founder of the LauraLynn children's hospice, Jane McKenna, has echoed Mr Irwin's concerns, saying recently St James's Hospital is "as bad as the Mater if not worse" as a location for the new hospital.
Ms McKenna, speaking in a personal capacity, said everyone she knows who has a sick child believes St James's was a poor choice.
"It's as bad as the Mater if not worse. I would absolutely agree with Jonathan Irwin," she said.
Ms McKenna thinks the greater amount of open space at the Dublin 15 location helps when it comes to treating sick children. It is important to look out at green fields, she added.