The government wants to expand cashless welfare card trials at other sites 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.

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

The government will also have another go at passing legislation to trial drug- testing for welfare recipients.

The divisive idea has already been rejected twice by the previous parliament.

But Finance Minister Mathias Cormann is defiant."We want to support and encourage Australians to deal with any barriers they are facing in terms of getting back into the workforce," Senator Cormann told the ABC.

"That is, of course, why we believe that through this drug testing trial, that we should assess whether there's better ways to channel Australians into treatment."

The Australian Medical Association opposes the trials, believing it will stigmatise people.

"It may actually make their chance of getting another job later much harder," AMA federal councillor Chris Moy said.

"The next thing is, there's actually no evidence from international trials that this actually works."

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

Labor says the bill is punitive and unfairly singles out welfare recipients.

Manager of opposition business Tony Burke said the legislation was just another government distraction when it should be focused on the slowing economy.

Construction boss John Setka is under mounting pressure to resign, as the Senate prepares to scrutinise draft laws to ban union officials who repeatedly break the law.

Senate Lambie, who holds a crucial swing vote, has declared she will eventually support the union-busting bill if Mr Setka does not stand down.

"I'm going to stay very solid on this - John Setka needs to resign," Senator Lambie told the Nine newspapers on Monday.

"Either he resigns now or these rules will come into place and he won't be able to stay on the line and he's going to go down anyway. Is it worth taking 1.4 million union members down with him?"

However, Senator Lambie said she would try to kill the bill in the coming fortnight of parliament if Mr Setka quits.

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