The rebel TD Patrick Nulty is to be expelled from the parliamentary Labour Party after voting against the Coalition on the Budget yesterday.
It was not until the fourth vote of the night, regarding the VAT rise to 23%, that the newly elected Dublin West TD finally crossed the floor to the Opposition.
He now automatically loses the Labour whip, but he insisted that he will not be resigning his seat, or his membership of the wider Labour Party.
Finance Minister Michael Noonan said he was disappointed to lose Deputy Nulty, but that it was a matter for the Labour Party.
"He's a Labour Party deputy, I hardly know him because he was a by-election victor," said Minister Noonan.
"It's really something for Labour Party people.
"We're sorry to lose anybody on either side."