The head of the Jack and Jill Foundation has said he has been sent two anonymous letters which he says proves the site of the new National Children's Hospital is inappropriate.
The letters, which are purported to be from senior officials, set out details of an overspend in the planning and design process at St James's Hospital in Dublin.
Controversy over the selection of the St James's site continues to mount, because of claims it does not have enough space for expansion or parking and due to its inaccessibility to patients from the rest of the country.
The Jack and Jill Foundation's Jonathan Irwin said he is concerned about one of the letters' claims that the same architects involved in the failed bid to build the hospital at the Mater are once again involved at St James's.
He said: "Our man says that they (the architects) were very definitely more expensive than all the other practices.
"What I would like them to do, now that they have the gig for this one, is to hand back the fees for the first one to make the pill of €40m down the drain and not a brick on the ground slightly more bearable."