Donegal TD Joe McHugh has resigned the Fine Gael party whip in a move which sees the Government lose its majority in the Dáil.
Mr McHugh earlier voted against the Government in the second stage vote in the Dáil on legislation to provide redress to homeowners affected by defective blocks.
This means that the Government's nailed down numbers would fall to 79, which is one short of a majority.
"I confirm that I am resigning the whip of Fine Gael and, while I do so with a heavy heart, I believe that it is the right decision," Mr McHugh posted on social media this evening.
Mr McHugh told the Dáil tonight he had not achieved what he wanted for his constituents leading him to vote against the Defective Concrete Blocks Bill.
He added that the redress scheme falls short in terms of accessibility and affordability.
He believes there were many shortcomings in the scheme and not enough Dáil time had been provided to debate it.
He spoke strongly in favour of allowing people to downsize their homes under the scheme but this was not included in the legislation.
The Tánaiste earlier told the Fine Gael parliamentary party it was regrettable that Mr McHugh could not vote with the Government.
However, Leo Varadkar said he had spoken to Mr McHugh and understood his feelings on the matter.
Mr Varadkar said he was confident that Mr McHugh would vote with the Government on other issues.
He said too that the Government would continue to have a working majority and it had not come close to losing a vote.
"My gut is telling me this second scheme is falling short for too many people," Mr McHugh said.
The Dáil passed the bill tonight with 74 TDs voting in favour and 69 against.
It is also anticipated that TDs Patrick Costello and Neasa Hourigan will return to the Government fold before the end of the year.
Neale Richmond, TD for Dublin Rathdown has told RTÉ's Drivetime that he did not expect the move from Joe McHugh and that it was very disappointing.
"This issue hasn't exactly been a new issue, we've been discussing and debating this with affected homeowners for months and years. I believe the package put together is a good one." Mr Richmond said.
He said that he rejected the notion that the Government was not listening to people affected by mica.
"I think we are right to pass this legislation today and I want to see the affected homeowners in a position where they can draw down the funds as soon as possible," Mr Richmond added.
In the Dáil, Paul Murphy of People Before Profit said that the Government "had just lost its majority" and asked if Minister for Housing Darragh O'Brien had "drawn any conclusions from that?"
He also said that the development was due to the campaign by affected homeowners who were present in the visitors' gallery of the Dáil.
