Funds which should have been used to build around 4,000 social and affordable housing units went unspent in recent years.
Figures obtained by Sinn Fein show that almost €1bn intended to be used to provide affordable homes, wasn't used between 2020 and 2022.
The Department of Housing blamed the halting of building during Covid 19 lockdowns as one of the primary reasons for the underspend.
But Sinn Féin Housing Spokesperson Eoin Ó Broin says if that was the reason, the same problem wouldn't have arose last year.
"Covid-19 is not the main cause of this underspend. If that were the case, then last year the underspend would have fallen dramatically as the Covid pandemic was over.
"The very opposite is the fact, in fact last year was the largest underspend and it's continuing into this year according to the latest figures from the Department of Finance.
"Darragh O'Brien is vert good at blaming everyone else for the housing crisis, when in fact he is the Minister."
