Australians deserve an explanation about Scott Morrison's decision to secretly swear himself into three ministerial portfolios while in government, the prime minister says.
Anthony Albanese is seeking advice over the constitutional legality of Mr Morrison's actions and is due to be briefed by his department after he arrives in Canberra on Monday afternoon.
"This is extraordinary and unprecedented," Mr Albanese told reporters in Melbourne on Monday.
He described the appointments as "the sort of tin-pot activity that we would ridicule if it was in a non-democratic country".
A report by The Weekend Australian claimed Mr Morrison secretly took on the health and finance portfolios when the COVID-19 pandemic reached Australia in March 2020.
The former prime minister's unprecedented move was in response to emergency measures under biosecurity laws and ensured he could administer health and finance powers given to former ministers Greg Hunt and Mathias Cormann.
Mr Morrison also later swore himself in as resources minister and used the power to overturn former minister Keith Pitt's approval of a controversial gas project off the NSW coast, news.com.au reported on Sunday.
Mr Pitt reportedly did not know the former prime minister had joint oversight of his portfolio.
It was "extraordinary" for Mr Morrison to keep the appointments secret from his cabinet colleagues, Sydney University constitutional law expert Anne Twomey said.
"That undermines the confidence in the functionality of the cabinet ... it does raise real issues about the ability of the (former) government to function, at least in its last couple of years," she told Sky News on Monday.
"It's not normally legally required for you to (disclose) these things but they form part of ... arrangements we have to make our governments operate in a transparent and open way, so there's been a real failure there."
Not even national cabinet was informed of Mr Morrison's actions, West Australian Premier Mark McGowan said.
In the interests of transparency it should have been made public and it was "odd" for Mr Morrison to decide not to do that.
"I don't understand how you can get sworn in and it not be revealed ... there needs to be a full explanation of these things," Mr McGowan told reporters on Monday.
Mr Albanese said what occurred under the Morrison government was contrary to the democratic Westminster system.
"The people of Australia were kept in the dark as to what the ministerial arrangements were - it's completely unacceptable," he said.
"We have a non-presidential system of government in this country, but what we had from Scott Morrison is a centralisation of power, overriding of ministerial decisions and all done in secret."
A spokesperson confirmed Governor-General David Hurley followed processes consistent with the constitution when he appointed Mr Morrison to the additional portfolios.
"It is not uncommon for ministers to be appointed to administer departments other than their portfolio responsibility," a spokesperson said in a statement.
"These appointments do not require a swearing-in ceremony. The governor-general signs an administrative instrument on the advice of the prime minister."
Any decision about whether to publicise cabinet appointments was a matter for the government of the day.
Nationals leader David Littleproud said he did not know about the former prime minister's actions, despite him being a minister in the Morrison government.
"That's pretty ordinary, as far as I'm concerned," Mr Littleproud said.
"If you have a cabinet government, you trust your cabinet."
