There will be no link between the proposed new prison and mental hospital in north Co Dublin, the Tánaiste, Ms Harney, said today.
In answer to questions from Fine Gael leader Mr Enda Kenny in the Dáil, Ms Harney said the facilities would have separate identities, separate addresses and separate entrances.
"There will be nothing in common between the two facilities," Ms Harney said.
She said the decision to place the two facilities beside each other was in part influenced by the availability of a single 150-acre parcel of land. She said other sites were considered and that such large tracts of land around Dublin were quite rare.
Mr Kenny pointed out that some bodies were concerned that mental health sufferers would be further stigmatised because the Central Mental Hospital was being located beside a prison.
Irish College of Psychiatrists has described the move as a "totally retrograde step".