Building work on a replacement for the Central Mental Hospital in Dundrum in Dublin may begin by the end of next year.
Minister of State with responsibility for Mental Health Kathleen Lynch said that An Bord Pleanála had granted the project Strategic Infrastructure Development status.
She said she was confident the project will proceed through the planning process and building can start by the end of 2015.
Interested parties now have seven weeks to make submissions to An Bord Pleanála on the project.
The first phase of the National Forensic Mental Health Project in Portrane in north Dublin will involve a new 120-bed adult hospital, along with a ten-bed forensic child and adolescent unit and a ten-bed forensic mental health intellectual disability unit on the same site.
Phase one is provided for under the Health Service Executive's capital plan.
Phase two is still at design stage and will eventually provide for new regional intensive care units in the eastern, southern and western parts of the country.