The estimated final cost of the Ballymun regeneration project has increased to €942m.
Comptroller and Auditor General John Purcell told the Public Accounts Committee that the original budget approved in 1999 was €442m.
Mr Purcell said that €290m was due to inflation.
He also told the committee that the cost escalation had led to a funding gap and he said that tight financial management should be prioritised.
Mr Purcell said that the target date of 2006 for completing the demolition and building work would not be achieved until 2012.
He said the original target had been optimistic and that better planning and risk management could have helped overcome this situation.
