The Friday hearing will complete a marathon three weeks of evidence from former coalition ministers, senior public servants and the independent watchdog.

The scheme ran from 2015 until 2019 and recovered $750 million using annual tax office data to calculate average fortnightly earnings.

Hundreds of thousands of Australians were affected and it led to several people taking their lives while being pursued for false, illegally raised debts.

The fourth block of hearings examined a 2017 investigation by the Commonwealth Ombudsman into the scheme, proposals to expand robodebt, the impact it had on victims and how it was eventually wound up.

Yesterday, the commission heard from two Centrelink employees who worked with customers affected by robodebt.

Luke Baker, an authorised review officer between 2014 and 2017, told the commission there was “no rationale” for how debts came up in the system.

“The premise of how the debts were raised seemed bizarre or magical,” he said.

“We would previously have something from the debt team to explain the debt but this was missing (in the robodebt program).”

He likened the scheme’s premise to raise debts as being “the emperor’s new clothes”, without substance or truth.

Baker said no training was provided to Centrelink staff about how to review decisions made by the averaging system.

Instead, staff were told in 2015 the new compliance system would recoup billions of dollars in debt.

“There was curiosity (among staff), about how there could possibly be that much outstanding debt to the Commonwealth,” Baker said.

He said employees felt frustration and grief that the computer-generated debt was so different to their common sense.

Yet despite raising issues with his superiors, Baker said senior department figures continued to say the system was legal “over and over again”.

“Each and every time we raised concerns … we were told the system was working as intended,” he said.

A second former employee – who worked for Centrelink for more than 20 years – told the commission she was criticised and dismissed when she tried to raise concerns about how debts were being calculated.

“Ms Smith” – a pseudonym used by the commission – worked in a customer service role and saw first hand the human impact of the debts.

“I was concerned that this process might not be getting it right for our customers, causing them stress and anxiety,” she said.

“I was quite upset that we might be incorrectly generating debts.”

After helping a number of distressed customers, Smith raised her concerns with higher levels of management.

Yet instead of addressing her concerns, the department instead formally cautioned her and she was not allowed to serve customers with debt-related issues.

The formal warning also told her to “behave in accordance with the APS (Australian Public Service) Values and Code of Conduct at all times”.

Smith felt confused about receiving such a serious caution when she had passed on customer feedback.

“I couldn’t believe that my workplace, that Centrelink, was causing this sort of harm and trauma to people,” she said.

The commission on Thursday also heard former acting ombudsman Richard Glenn doubted the lawfulness of the scheme after his team investigated the human services department running it. 

Yet he ultimately decided not to refer the department to the Administrative Appeals Tribunal.

Glenn admitted he would have made a different decision knowing what he does now about the scheme.

“My thinking was influenced by the fact that I couldn’t make a clear determination one way or the other about legality,” he said.

“The advice that I was receiving from the team was that they were concerned, but we couldn’t land a crisp, contrary view.”

The commission previously heard the department had misled Mr Glenn’s office during the investigation by withholding key documents that flagged issues with the scheme’s legality.

A final report will be handed down by the end of June, after the commission was granted an extension to its April deadline.

-with AAP