The Government has decided to shift the location of the Department of Community, Rural and Gaeltacht Affairs from Knock, Co Mayo, to nearby Charlestown, following An Bord Pleanála's rejection of its original plans.
The decision means land bought at Knock by the Office of Public Works will lie idle for now, and that a new site will have to be purchased in Charlestown, the Minister, Eamon Ó Cuív, said.
However, the Knock property will "not go to waste".
"I have no doubt but that over the next 10 to 20 years we will find plenty of uses for it. Knock airport is going to develop."
Extra property will now be leased in Tubbercurry to house 30 more civil servants who have agreed to move from Dublin or other locations to join 70 department staff already temporarily housed there.
The Government's plans to build a new office at Knock airport were dashed when An Bord Pleanála ruled that it would be remote from "the normal range of services and facilities" and remote from any town.
The development would give rise to unsustainable forms of commuting and would contravene Mayo's development plan, the board ruled when it considered an appeal by Peter Sweetman and Associates of Rathmines, Dublin.
Last night, Mr Ó Cuív said he was confident a Charlestown office would get planning permission, since the town had been specifically mentioned in the board's final ruling.
The changes mean a final home for the decentralised department would not be ready now for "about two years", the Minister said.
