More than €150 million has been spent on Dublin's Metro up to the end of last year - despite no "significant" physical work.
An estimate of the project - which would run from Swords, through the airport and into the city centre - puts the cost at around €9.5 billion
The underground rail system has faced significant delays over the past two decades.
Speaking at the Public Accounts Committee, its chair. Brian Stanley, says the cost of preparatory works are "astronomical.
"You say that he projected cost of Metrolink before the preparation work would be in the region of €300 million, and we have blown €150 million on Metro north.
"This means that we will have spent almost half a billion euors on the metro before we even send a JCB on to the site."
The €9.5 billion Metrolink is set to run from north of Swords to Dublin Airport, then on to Ballymun, Glasnevin, O’Connell Street and St Stephen’s Green before terminating at Charlemont Street, with 16 stations in all.
Minister for Transport Eamon Ryan has previously said he remains confident that the project would receive planning approval this year and be built by the early 2030s.
