Households stand to lose hundreds of dollars as a result of the Turnbull government's two-year freeze on family tax benefits, Labor says as it ramps up its attack on crossbenchers who waved through welfare cuts.
The opposition is accusing One Nation and the Nick Xenophon Team of selling out battlers after they agreed to support the government's trimmed-down package of cuts.
But for one outspoken senator, the social security cuts do not go anywhere near far enough.
"Welfare should be for poor people, not for people who are comfortable," Liberal Democrat David Leyonhjelm told reporters in Canberra on Thursday.
"The government has got very small balls when it comes to middle-class welfare and they need their balls to be enlarged, so I'm doing it for them."
The senator's sights are set on chipping away at increases to childcare subsidies, which will be debated in parliament on Thursday.
Opposition Leader Bill Shorten said family tax benefit cuts that were passed overnight would mean single-income households on about $60,000 with two primary school-aged children will lose up to $440 over the next two years.
"Families with school-aged children stand to lose scarce dollars which help them make ends meet," he told reporters at Parliament House.
His Labor colleague Doug Cameron launched a spray against Pauline Hanson for backing the welfare cuts.
The One Nation leader was merely reciting from a cheat sheet typed up by the Liberal Party, he said.
"She claims she's a supporter of the battlers but her actions demonstrate - day in, day out - that she has not got one care, not one iota of concern, for the battlers in this country," Senator Cameron said.
Nick Xenophon and his senators did not escape the opposition's anger, either.
The government had combined a $1.6 billion boost to childcare and $5.6 billion in welfare cuts in a single omnibus savings bill, but on Wednesday chose to split it and drop a number of cuts after acknowledging certain defeat.
The upper house passed the welfare bill without amendments just after midnight on Thursday.
It now goes to the lower house.
Family tax benefit rates will be frozen for at least two years to help pay for childcare under the new plan.
Finance Minister Mathias Cormann denied the government was "ripping money out of people's pockets", saying no family would receive a lower level of payment under the changes.
Senator Hanson rejected Labor's claims she was selling out struggling families but argued the nation needed to rein in its finances.
The government expects the measures in the bill to generate $2.4 billion in savings over the forward estimates, building to $6.8 billion in the medium term.
It will pause indexation on family tax benefits for 24 months from July 1, saving about $1.4 billion over two years.
It has also backflipped on a commitment to boost fortnightly family tax payments to offset the abolition of end-of-year supplements.