The Government's help-to-buy scheme, which is paid to first-time buyers of newly built homes, is now likely to cost far more than originally expected.
The initiative, which was launched in the Budget, provides a grant of up to €20,000 for home buyers.
Based on average applications to date the cost of the scheme so far this year could be €56m.
The Department of Finance had made a provision of €50m for the scheme in the Budget for the full year of 2017.
In a Dáil reply to Fianna Fáil's finance spokesman Michael McGrath, Minister for Finance Michael Noonan said by 7 March 230 applicants had received payments of €3.48m.
This works out at approximately €15,000 per applicant.
There are currently 3,753 applications which have been made for grants.
On the basis that each applicant would receive €15,000, the cost to the State so far would be €56m by 7 March.
In his Dáil reply, Minister Noonan said he expected a number of retrospective cases to be made early in 2017. He added that this was in line with Budget estimates.
"Given the way it was set up as a demand-led scheme, the Government has no control over the final bill," Deputy McGrath said.
He said he expected the Minister for Finance to publish an independent impact assessment of the scheme which has already been commissioned.
"The Government should have carried out such an impact assessment before putting this scheme in place and it is vital such an assessment is available before the Budget in October," Deputy McGrath added.
In response to the Dáil reply, a spokesman for the Department of Finance said the scheme was there to stimulate house building and that the supply of housing was the Government's number one priority.
He said the scheme would also stimulate economic activity.
However, he added it was "difficult to extrapolate from these figures as there is no guarantee that people who have made an initial application for the scheme will get mortgage approval from a lender or find a house that suits their needs or their level of affordability."