Pauline Hanson has killed off the federal government's hopes of the Senate passing controversial changes to welfare payments tied to childcare reforms.
The Turnbull government has bundled together 16 welfare cuts, including a reduction to family tax benefits, in an omnibus bill, designed to save billions of dollars that would be redirected into childcare subsidies and disability funding.
The votes of Senator Hanson and her three One Nation colleagues in the Senate were critical to the passage of the legislation.
But the One Nation leader said the cuts were too hard, too broad and too deep for Australian families.
She urged the government to turn its attention to tax-dodging multinational corporations.
"The coalition needs to realise that before those with the least are asked to tighten their belts, those multinationals with the most need to start paying their way," she said in a statement.
Earlier on Tuesday, welfare groups painted a bleak picture of the fallout if Australians are forced to absorb $5.6 billion in social security cuts.
"To take even more away from those who are struggling already to live below the poverty line is like feeling like you're lying in the gutter and you've just been kicked in the guts," St Vincent de Paul Society chief John Falzon told reporters in Canberra on Tuesday.
Social Services Minister Christian Porter said negotiations with crossbenchers had reached a sensitive point with senators pulling in different directions.
"I'm confident we will find that path through but it is a little bit of a threading the eye of the needle exercise and rather delicate," he told Sky News.
"We don't put things up expecting not to succeed. But equally, we accept that we will not be able to succeed on every single savings measure."
A government-dominated Senate committee on Tuesday has recommended the legislation be passed.
In a report tabled in parliament, it said it acknowledged concerns about the legislation but considered the changes to welfare would better target government payments while providing a "fair and reasonable safety net for those who need it".
In separate dissenting reports, Labor and the Greens recommended that the Senate reject the legislation.
Labor recommended the government separate the child care changes from the welfare cuts.
It wants the government to scrap the cuts altogether and fix the child care reforms so disadvantaged children still have access to two days of early education a week.