Labor and the Greens have accused their Coalition Senate colleagues of ignoring "overwhelming" medical evidence against drug testing welfare recipients.

Key points: Coalition senators recommend welfare drug testing bill be passed by Upper House

Coalition senators recommend welfare drug testing bill be passed by Upper House Labor says trials "should not proceed in the face of overwhelming opposition" from experts

Labor says trials "should not proceed in the face of overwhelming opposition" from experts Program will "further isolate and stigmatise" drug users, Greens argue

A Senate committee has investigated the Government's suite of changes to welfare payments, including a drug testing trial of 5,000 new recipients on Newstart and Youth Allowance.

People testing positive would continue receiving financial assistance, but 80 per cent of their welfare would be placed on a debit card that can only be used on essential items such as rent, child care and food.

If a person tested positive a second time, they would be referred to a medical professional and potentially have to pay for the cost of the test.

Coalition senators have now recommended the bill be passed by the Upper House.

"Critics of the introduction of a drug testing trial have stated that there is no evidence that drug testing will achieve the desired outcome," Government senators conceded in their report.

"The committee heard that, while information relating to the cost and detection rates of the New Zealand drug testing program is available, outcome data is not available."

Proposal 'likely to exacerbate' issues, Labor says

However, Government senators have accepted the evidence of the Department of Social Services about the merits of the plan.

That has raised the ire of the federal Opposition.

"It is the view of Labor senators on this committee that the proposed drug trials should not proceed in the face of overwhelming opposition from addiction medicine specialists and other experts," senators Lisa Singh and Murray Watt wrote.

"The committee heard that there is already insufficient treatment available to Australians who are seeking treatment for substance abuse issues, and that the Government's proposals are likely to exacerbate this issue.

"Labor senators on this committee are deeply troubled by revelations that the Department of Social Services does not know the length of existing waiting lists for drug and alcohol treatment in the three sites for the Government's drug testing trial."

The Greens labelled it as a failure "to understand, and indeed actively ignores the medical nature of addiction and the complex biological, psychological and social underpinnings of drug addiction".

"Placing people on income management or withholding payments for people who test positive to illicit drugs if they don't comply will not help them to recover from addiction or to stop using drugs, but rather further isolate and stigmatise them," Greens senator Rachel Siewert said.

Three trial sites have already been named, despite the legislation having yet to pass Parliament — Canterbury-Bankstown in New South Wales, Logan in Queensland and Mandurah in Western Australia.