Greens senator Rachel Siewert is to make a last-ditch attempt to prevent a trial of the cashless welfare card, saying people remain deeply concerned about the process.

Under the cashless system proposed by mining magnate Andrew Forrest, 80 per cent of a person's payment would be placed on a bank card that cannot be used on alcohol or gaming.

Legislation was passed in October last year to establish three trial sites for the card.

Ceduna in South Australia and Western Australia's East Kimberley have already committed to the trial, with the final site yet to be determined.

However, a number of WA shires have expressed an interest, including neighbouring Leonora and Laverton in the northern Goldfields.

Senator Siewert said she would introduce a disallowance motion in Federal Parliament next week to block the regulation required for the first trial, in Ceduna.

She said she did not believe there had been adequate consultation with the communities involved.

"I'm still getting emails expressing deep concern about the overall process," Senator Siewert said.

"People are concerned about reports the Government plans to roll this out further."

Senator Siewert said she would require the majority of the Senate to support her disallowance motion, but hoped Labor would rethink its support for the plans.

"There's a whole range of problems with this approach that the Government hasn't adequately answered," she said.

"They say this is a so-called trial, yet they haven't put in the processes that would adequately enable them to compare it to a different sort of approach.

"In a community where, for example, they don't have the cashless welfare card, but they do have [other] new services."

Siewert should respect parliamentary mandate: Tudge

Assistant Social Services Minister Alan Tudge said he was disappointed Senator Siewert planned to move a disallowance motion.

"The Parliament passed the cashless welfare card legislation with bipartisan support," Mr Tudge said.

"She should respect the mandate of the Parliament.

"At the very least, she should have the decency to meet and face the local leaders on the ground that have co-designed this trial with the Government and want this reform to go ahead."

Mr Tudge said there were no plans to roll the cashless welfare card out across Australia.

"We're taking it one step at a time. We will hold the trial, assess it and make any further decisions then," he said.