The Government has won a key vote on the Social Welfare Bill in the Seanad by just three votes.
Thirty-one Senators voted in favour of the bill, with 28 voting against.
Labour Senator James Heffernan voted against the bill, which will cut child benefit and some care grants.
He said a solemn pledge was made by Labour not to cut child benefit, and that the pledge is now broken.
He said he could not in good conscience be part of that, when there was a choice to tax high earners. Going after carers and children is inherently unfair, he said.
However, he said he would remain a "Labour man" and he did not take this decision lightly
Concluding the debate, Social Protection Minister Joan Burton said it was not possible to exclude the cuts to respite care grants without derailing the entire bill.
Ms Burton said she is open to proposals to provide more care services through community employment schemes.
The final stages of the bill will be debated again in the Seanad tomorrow and it is set to become law early next year.