The Labour Party has been dealt a damaging blow over the budget after the chairman rebelled and refused to back social welfare cuts.
Colm Keaveney became the fifth TD from the party to revolt in the 20 months of coalition when he voted against the Government.
"We have failed in the negotiations to secure a very important value of the Labour Party and that's to protect people in society who can't protect themselves," Mr Keaveney said. "I don't think this Government are catching the appetite of the nation and the people out there want to see fairness and they want to see a more just society."
Mr Nulty welcomed the chairman's decision to oppose the social welfare bill. "This is an unfair budget, which breaks Labour promises," Mr Nulty said. "The measures contained in the bill, such as the cut to the respite care grant and the cut in child benefit, are not acceptable to those who voted Labour."
Labour has come under constant attack since Budget 2013 was unveiled last week with opposition TDs accusing the party of selling out on its policies to prop up its senior partner Fine Gael. Fianna Fail, Sinn Fein and members of the United Left Alliance launched a three-pronged assault on the party, accusing it of turning its back on pre-election promises, which included a vow to leave child benefit payments untouched.
East Galway TD Mr Keaveney was reportedly one of several Labour backbenchers voicing concerns about the budget, saying it went against the party's policy.
"It's not about personalities, it's about policies and I know there will be personal repercussions for me," he told Newstalk Radio. Mr Keaveney said he could not return to his constituency and look members of the public in the eye while supporting the austere measures.
He insisted the Labour parliamentary party was a separate entity to the Labour Party of which he is chairman.
He said he represented all Labour members including those who, before its election to Government, went from door to door, promising the party would protect the vulnerable.