The unpublished report into the location for the new National Children's Hospital says that St James's Hospital in Dublin best meets the criteria to be the adult co-located hospital.
The Dolphin Report says it has the broadest range of national specialities.
According to the findings, seen by RTÉ News, co-location with an adult academic teaching hospital is essential, while tri-location with an adult and maternity hospital is optional.
The 80-page report says that from a design and planning perspective, the sites adjoining Connolly Hospital and the Coombe Hospital offer the best potential for future expansion and a landscape setting.
However, the report says that Connolly Hospital would need very substantial investment of human and capital resources to develop over time into an adult tertiary hospital, with critical mass supported by leading-edge research facilities.
Even if such resources could be made available, it says it could take several decades to achieve such high standards of clinical and research excellence.
The report also says St James's has an excellent research and education infrastructure.
The Coombe Hospital plan is on a site off the South Circular Road on 20 acres of land near the Luas Red Line.
In 2010, St James's Hospital secured planning permission for a nine-storey hospital building, one storey higher than its current paediatric hospital proposal, although the scale of the proposed children's hospital there would be much bigger than the private hospital that was being planned for two years ago.
Minister for Health James Reilly is currently preparing a memo for Cabinet with a proposal for the best location, based on an analysis of the Dolphin Report.
It follows a meeting late last week with Taoiseach Enda Kenny and Tánaiste Eamon Gilmore where the report was discussed.
The Cabinet may discuss the issue at its meeting next week.
Meanwhile, Dublin City Council has said that it notes certain comments made in relation to possible planning issues with a proposed location for the new hospital in Dublin city.
It said that no one can be definitive on the planning aspect of any site at this stage because the final arbiter will be An Bord Pleanála.
This applies to sites both within and outside the jurisdiction of Dublin City Council.
However, the council also said it is satisfied that the proposals within the city boundaries can all work from a planning and infrastructure perspective and in the process, avail of the public transport and other facilities of a city centre location in a capital city.
Fianna Fail's Health Spokesperson Billy Kelleher and his Sinn Féin counterpart Caoimghin Ó Caoláin have both called for the publication of the Dolphin Report.
Deputy Ó Caoláin said that in the interim while the new hospital is being designed and built, the existing children's hospitals must be properly funded.