Government Services Minister Stuart Robert announced on Tuesday the department would stop issuing debt notices based on averaged income data from the Australian Tax Office and review hundreds of thousands of robodebts, a fortnight out from a landmark test of the legality of scheme in court.

The minister has since refused to answer further questions, although his cabinet colleague Christian Porter confirmed the backflip was preceded by legal advice.

A script circulated to Centrelink calltakers shows the government is expecting calls from clients who insist they were averaged and demand a refund.

They have been told to tell clients to wait for Centrelink to contact them instead.

"If your review was subject to averaging it will be identified and we will be in touch. You could locate payslips or bank statements to prepare for the reassessment," the suggested dialogue said.

La Trobe Law School senior lecturer Darren O'Donovan said the decision to overhaul the controversial program had raised more questions than answers.

"Many community legal centres will once again be fielding inquiries from people concerned about where they stand," Dr O'Donovan said.

He said there needed to be be a reference group set up to create a "road map" for the program going forward.

There was also a question mark hanging over debts beyond the legal retention period.

"Are they absolutely ruling out debts which go back to 2009, 2010, 2011?" Dr O'Donovan said.

It was also unclear how the department would source employment records.

"Is the minister saying they're going to go out and make section 192 requests that they used to do. The whole point [of robodebt] was section 192 was a slow process. They went from 20,000 debts to hundreds of thousands by eliminating direct requests to employers for information.

Going back to that process undercut the whole rationale for robodebt, Dr O'Donovan said.

"One of the reasons the department embarked on this was to lower the cost-benefit ratio on debt decisions. I think there's a huge question mark over the economics of this," he said

The Not My Debt campaign, which has collated and shared stories of people slapped with robodebt notices, is concerned about how the process is playing out.

"We believe that the department has massively-understated the nature and extent of the maladministration to date," a spokesperson said.

"Of course, we don't believe that the remediation process can be done efficiently or cost-effectively - and we fear that this will be just another counter-productive effort to throw good money and resources after bad policy."

Not My Debt has called for the program to be randomly, independent audited.

"Ultimately, we believe that all reverse-onus compliance debts will need to be fully-reversed - including those manually raised under the pilot and Interim processes - with full reimbursement of monies collected under circumstances of false pretenses and coercion - and that interest and compensation may be in order in many cases," the spokesperson said.

Gordon Legal's Peter Gordon also called for the government to refund money, after their class action was launched on Wednesday.

He said there was a fundamental unfairness in the system that meant only certain people had been able to fight their debts.

"There are a number of people who have proved the government wrong in individual assessments," Mr Gordon said.

"They tend to be the people who've got the wherewithal, the courage, the experience, the contacts and the family contacts to enable them to argue the toss. What about the people who can't? Who are on unemployment benefits, who don't have that sort of access, who are frightened by the government, who are scared to take this sort of initiative.

"This government has preyed upon literally the most vulnerable people in our community and a number of them we know would never consider contacting lawyers because they just don't feel empowered to do it."