Scott Morrison's decision to secretly take on extra ministerial portfolios has been labelled as corrosive of trust in government.
A report by former High Court judge Virginia Bell into the multiple ministries found the secrecy surrounding the appointments he took on as prime minister was "apt to undermine public confidence in government".
"Once the appointments became known, the secrecy with which they had been surrounded was corrosive of trust in government," the report said.
"Given the parliament was not informed of any of the appointments, it was unable to hold Mr Morrison to account in his capacity as minister administering any of these five departments."
Mr Morrison appointed himself minister of health, finance, industry, science, energy and resources, treasury and home affairs without the knowledge of most of the designated ministers.
It was also revealed in the report on Friday he sought advice on appointing himself to the agriculture, water and environment portfolio but did not proceed with it.
While the former prime minister said he took on the health and finance roles due to the COVID-19 pandemic, Ms Bell said this was unnecessary.
The report said while then-health minister Greg Hunt was told of Mr Morrison's moves, the federal health department was not.
It said Mr Morrison could have authorised himself to act as health or finance minister "in minutes", were the ministers to have been incapacitated due to COVID-19 in early 2020.
Ms Bell said Mr Morrison's other three ministries were in a "different category".
"These appointments had little, if any connection to the pandemic," she said.
"Rather, Mr Morrison was appointed to administer these departments to give himself the capacity to exercise particular statutory powers."
Prime Minister Anthony Albanese, whose cabinet is set to approve transparency measures on Monday, said the previous government had operated in a "cult of secrecy".
"(The secret ministries) were unprecedented and they were wrong. However, members of the former government and current opposition enabled this culture of secrecy," he told reporters in Canberra.
"That is the characteristic of the Morrison government. After nine years of chaos, a dysfunctional government has now been replaced by a dysfunctional opposition."
While he did not say whether Mr Morrison should resign his Sydney seat of Cook, the prime minister said his predecessor had misled parliament.
In a statement, Mr Morrison said he had carried out his responsibilities as prime minister in the national interest.
"These decisions were taken during an extremely challenging period, where there was a need for considerable urgency," Mr Morrison said.
"Criticisms of my decisions have been made after the event and with the benefit of this perspective."
Mr Morrison said he would continue to serve in federal parliament, noting he was "pleased" the inquiry - which he engaged in via lawyers - had concluded.
Shadow attorney-general Julian Leeser said the opposition had noted the findings laid out in the report.
"The report ... makes a number of sensible recommendations for improving the clarity and transparency of ministerial appointments," he said,
"The opposition will consider any proposed legislation flowing from the report through its usual processes when it is presented to the parliament."
Ms Bell recommended six changes to be made including legislation requiring public notifications of the appointment of ministers.
She also recommended publishing details of which ministers were appointed to administer departments and outlining different responsibilities when more than one was appointed to the same department.
Mr Albanese said he would take action to ensure "this breach of trust will never happen again".
The report confirmed Mr Morrison had only used his extra ministerial powers to veto the PEP11 resource exploration project off the NSW coast.
Ms Bell also took aim at Mr Morrison's decision not to tell ministers of his appointment to their portfolios.
"It is difficult to reconcile Mr Morrison's choice not to inform his ministers of the appointments out of his wish not to be thought to be second guessing them," the report said.
© AAP 2022