Louth TD Peter Fitzpatrick has resigned from Fine Gael.
It leaves the minority government's numbers for passing key votes looking even more shaky.
Deputy Fitzpatrick had been feeling increasingly isolated in Fine Gael, saying his views weren't being listened too - despite backing the government through the years of austerity policies.
He released a statement on twitter last night:
Press release pic.twitter.com/7NEIZ0ZKXo
— Peter Fitzpatrick (@PFitzpatrickTD) October 1, 2018
Mr Fitzpatrick was a vocal advocate for a No vote in the abortion referendum, putting him at odds with most of his party colleagues.
He confirmed weeks ago he wouldn't be seeking a nomination to run as a Fine Gael candidate in the next election, and confirmed last night he was resigning from the party to continue as an Independent TD.
Taoiseach Leo Varadkar said a few weeks ago Mr Fitzpatrick had committed to staying in the party until the end of this Dáil term, and that he regrets his change of mind.
His departure may make things difficult for the government on key votes.
It needs 57 votes to be sure of passing anything as long as Fianna Fáil abstain, and the Confidence and Supply agreement was built around that number.
But the government now has only 55 - with Fine Gael TDs, the 4 Independent Alliance members and Independent Ministers Denis Naughten and Katherine Zappone.
Independents Sean Canney and Michael Lowry also support the government on certain votes, and that could be crucial to passing next week's budget.
Fitzpatrick's resignation certainly does little to help Leo Varadkar as he enters negotiations with Micheál Martin on renewing the deal that keeps the government afloat.
Reporting by Sean Defoe