The government expects one in 10 people to test positive for drugs as part of the proposed trial for drug-testing welfare recipients.
Meanwhile, Newstart recipients visiting Parliament House said the prospect of drug-testing welfare recipients was discriminatory and blames them for their own poverty.
Social Services Minister Anne Ruston confirmed on Tuesday the government intends to introduce the legislation to drug test welfare recipients in three trial sites, with 5000 people to be tested.
Of the 500 people expected to test positive, the government believes about 150 will test positive again at a second test 25 days later and then become eligible for rehabilitation support.
Senator Ruston stressed on Tuesday that those who failed drug tests wouldn't have their payments cancelled or reduced, but the aim was to reduce the amount of cash available to them so it couldn't be spent on drugs.
The government has pledged $10 million in support services to go along with the plan but political fighting over whether it would help or hurt those with addiction issues continued on Tuesday.
Welfare recipients at Parliament House on Tuesday savaged the plan. Brisbane woman Imogen Bunting labelled the plan "discrimination by socio-economic status".
"Isn't it interesting that they are deciding that modern day policing is to be done by public servants ... there's no reasonable cause, no reasonable suspicion that a police officer would need to undertake such a drug test," she said.
Ms Bunting said the prospect of being put on a card, which quarantines 80 per cent of her payment, was scary.
"I cannot abide by the default that to get what I need to live when I'm down and out in this country, I'm sanctioned."
Ms Bunting, along with three others from the Unemployed Workers Union, had travelled to Canberra to meet with MPs and lobby for a raise to the rate of Newstart, along with other issues related to welfare.
While the advocates expected to meet with more than 35 MPs from across the political spectrum while they were here, so far Minister Ruston and Human Services Minister Stuart Robert had declined the invitation to meet with them.
Despite having work two days a week, Ms Bunting said she could no longer afford to pay rent and was living in her car and couch surfing, but often felt her car was safer than staying in hostels or other options.
Labor opposes the plan, with government services spokesman Bill Shorten saying that unless an addict is ready to change, drug-testing and income management won't make a difference.
One Nation Senator Pauline Hanson, who has already backed the government on the issue, said on Tuesday that fellow crossbench senator Jacqui Lambie should support the bill because she knows what it is like to have a family member on drugs.
"Her child has been on drugs and you wouldn't knock back something that could possibly help people like her son," Senator Hanson said.