Labor elder Doug Cameron has given welfare changes before the Senate both barrels, even though plans to drug test thousands of unemployed being dropped.
The Turnbull government suspended plans to drug test 5000 welfare recipients from January next year after the Senate shot down the idea.
But the backdown has done little to satisfy Labor, who oppose all but the most procedural changes contained in the 200-page bill.
"(This bill) has measures that will expose vulnerable people in our communities and increase hardship and suffering," Senator Cameron told parliament on Thursday.
"It attacks the most disadvantaged people in our community. It tightens the screws on people that are already struggling to make ends meet."
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Social Services Minister Christian Porter is confident the remainder of the bill will sail through parliament, with support from the crossbench.
But it can't rely on support from Labor or the Greens to tighten exemptions for drug and alcohol dependence, increase wait times for unemployment payments, or axe the wife pension and bereavement allowance.
"This bill targets vulnerable people for menial savings," Greens Senator Rachel Siewert said.
"We cannot afford to erode our social safety net."
The opposition will only back introducing a demerit point system for people who persistently dodge job-seeking obligations if greater safeguards are put in place.
Liberal backbencher Slade Brockman bemoaned the drug testing being put on ice.
"Obviously the trial will not go ahead at this point. I think that's a shame and the government certainly does remain committed to it," he told the chamber.
"We will continue constructive discussions with the cross bench and seek to progress the drug testing trials through separate legislation."
Senator Cameron derided the drug tests - which Prime Minister Malcolm Turnbull heralded as a policy based on love - as flawed and hateful.
"It is a blatant attack on the most vulnerable people in our community with no basis in evidence," he said.
