Porter said unemployed people with drug problems were cutting themselves off from job opportunities in the construction, mining and transport industries, which regularly tested staff.
The Government plans to start the two-year trial in three areas from January, with about 5000 people affected including about 1750 from Canterbury-Bankstown.
Labor and the Greens are opposed to the trials so the Government will need support from the Senate crossbench to get its programme off the ground.
Shadow attorney-general Mark Dreyfus says there is no evidence the tests will lead to a reduction in drug use.
"On the contrary, it's likely to lead to an increase in crime, an increase in inequality and further harsh treatment of welfare recipients," he told ABC radio.
The plan, which has been widely criticised since it was announced in the May budget, will test Centrelink recipients for illicit substances including P, ecstasy, marijuana and opioids.
Anyone who tests positive will have 80 per cent of their payments quarantined in a cashless welfare card.
Those who fail more than once will be referred to medical professionals for assessment and treatment.
Depending on the type of test, it will either take place at a local Centrelink centre or a nearby facility.
The Government says all tests will be done in private by a "suitably qualified representative" from a contracted drug testing provider and the results will not be shared with police.
Porter is unapologetic about catching out one-off users, saying there is no safe or lawful amount of drug intake.
- AAP
