Documents detailing robodebt advice handed to Scott Morrison when he was social services minister have been kept secret, citing their release could "substantially" harm the public interest.
Minutes of a meeting between senior officials within the Human Services Department - now Services Australia - discussing the agency's online compliance program in early 2015 will remain hidden for now.
A decision made by the Commonwealth Ombudsman's office this month argued against the public release of the document after it was requested in a question on notice by a senate committee.
Labor's government services spokesperson Bill Shorten has called on the federal government to "do the right thing" and release the sought-after documents.
The meeting minutes were handed to then-social services minister Scott Morrison months before it was publicly announced in 2015 as a government initiative to recuperate the federal budget.
The government watchdog said it received the minutes in early 2017 but would not release them because it threatened to affect their ability to oversee departments and agencies.
'Robodebt' is the popular term used to describe the agency's debt recovery program.
It raised compliance notices against more than 430,000 current and former welfare recipients using an "income-averaging" system to spread a person's reported taxable income across every fortnight of the year.
In a lengthy response, the Commonwealth Ombudsman argued its role was predicated on "almost unfettered access" to information and documents from the agencies and that required discretion to maintain trust.
It added it did not have the power to compel agencies to hand over documents.
"Without wide-ranging access to the information of the agencies we oversee, and the trust of those agencies that their information will be kept confidential, our ability to perform our functions and achieve our purpose would be severely compromised," the ombudsman's response said.
"Having considered the possibility of disclosing the DHS Executive Minute very closely, and weighing the competing public interests, the office's strong preference is not to provide a copy of the minute.
"The office has significant concerns that disclosure would be likely to harm the public interest substantially by undermining the effective future performance of the ombudsman's functions."
Mr Shorten said the public deserved to know in which circumstances the unlawful policy was brought into effect.
Government Services Minister Linda Reynolds should release the document herself, he said.
"This just proves there is a public interest in revealing robodebt's sordid origins," Mr Shorten said.
"The ombudsman has belled the cat on Linda Reynolds' lies that she has a right to cover up this information forever.
"The government should do the right thing and release this information to the Australian public."
In June, the federal government was ordered to pay nearly half a million Australians affected by the controversial robodebt scheme a total of $1.8 billion, including $112 million in interest.
The government agreed to pay back $751 million and wipe further debts that had been raised but not yet collected under the scheme.
The payout to members of the class action was agreed to on the basis the government not, nor any of its officers, admit it was legally liable.
It comes as a four-year fight to access the documents to do with the scheme is being held within the Administrative Appeals Tribunal.
The case centres on denied requests under freedom of information laws for the documents by digital rights advocate Justin Warren.
He first requested the release of the documents in 2017 but has been knocked back several times by the former department, now known as Services Australia.