The Government is facing planning hurdles over its decision to select St James's Hospital as the new site for the €600m children's hospital.
As Health Minister James Reilly unveiled the Government's decision to award the project to St James's, he admitted there was a "moderate" risk the development could suffer the same fate as the Mater by failing to get planning permission.
St James's has said that it can build the project for €478m, but Dr Reilly said that this estimate was "tight".
Around €200m is earmarked for the hospital from the National Lottery. Most of the remaining funds will come from the capital budget.
It has emerged that it will be at least nine months before the project is ready to go to planning permission.
A detailed design is not expected to be completed for the 108,000sqm building until next August, with a planning decision expected about six months later, in early 2014.
The original cost of the hospital on the Mater site was €650m, but Minister Reilly refused to be drawn on the bill for the St James's project, on the ground of commercial confidentiality.
It is expected that the project will be completed in 2018.
The Mater and Rotunda hospitals expressed disappointment that the Government had not re-selected the Mater.
"Six years of planning have already gone into our site.
"We could have delivered a new children's hospital by 2016, but yet the sick children of Ireland now have to wait a further two and a half years for what is their right," said Mater chairman John Morgan.
The decision to locate the national children's hospital on St James's hospital campus was welcomed by Opposition and Government politicians.
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