The coalition wants to expand cashless welfare card trials across the country and has the backing of key Senate crossbencher Jacqui Lambie.

"I've always been a big supporter of the cashless welfare cards - I've seen the result that has had," Senator Lambie told reporters in Canberra on Monday.

"I will say this, though, get those algorithms right because quite frankly it's taking you way too long, get it moving."

Cashless welfare cards, which quarantine 80 per cent of payments so they can only be spent on essentials, are currently in use across four trial sites in South Australia, Western Australia and Queensland.

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Deputy opposition leader Richard Marles confirmed Labor remained opposed to a nationwide rollout of cashless welfare cards.

"It's for the government to actually explain the basis on which it sees a benefit in this being rolled out," he told the ABC.

"The auditor-general has been scathing about the effectiveness of this where it has been tried. The evidence that the government cites is really skinny."

However, One Nation leader Pauline Hanson is confident the cards are working.

"It's actually cut back on domestic violence, people on drugs, people who are actually on alcohol. Kids are going to school, so it has worked in areas," she said.

Senator Lambie will also support legislation to drug test welfare recipients, but only if federal politicians are also screened for illicit substances.

"If you've got nothing to hide up there in that big white house, then it's now your turn to go and do those random drug and alcohol testing," she said.

"What's wrong with you people, what, might miss a few wines after 8 o'clock of a night time, will we? That'll keep the backbenchers in line."

Nationals backbencher Barnaby Joyce has no qualms about MPs being drug tested.

"I don't think it's right that someone should be passing laws to stop people sticking crap up their nose and then doing it themselves," he told the Seven Network.

"I've got absolutely no problems whatsoever with drug-testing of politicians."

Mr Marles is also happy to be drug tested but does not want the disadvantaged to be persecuted under the policy.

"I think there is an indignity in what is being proposed here," the deputy opposition leader said.

"We're for anything which stops people taking drugs, and anything which gets people into work, but we've got to see what the evidence for this particular proposition is.

"It's a real problem if we're seeing the most vulnerable in our society being persecuted."

The two-year drug testing trial would be rolled out in three locations - Logan in Queensland, Canterbury-Bankstown in NSW and Mandurah in WA.

AAP