Scott Morrison created a legal "mess" by secretly taking control over a handful of portfolios, constitutional law experts warn.
Governor-General David Hurley confirmed he handed the former prime minister power over multiple departments without an official swearing-in ceremony.
Prime Minister Anthony Albanese was due to receive urgent briefings from department officials late on Monday, after earlier accusing his predecessor of running a "shadow government".
Nationals frontbenchers have hit out at Mr Morrison, but the former prime minister claims he is unaware of the criticisms because he has not "engaged in any day to day politics" since losing the election.
A spokesperson for Governor-General Hurley on Monday confirmed Mr Morrison was indeed made minister in multiple portfolios via an "administrative instrument on the advice of the Prime Minister".
They did not reveal which portfolios Mr Morrison had assumed control of, but insisted all appointments were made "consistently with section 64 of the Constitution".
"The Governor-General, following normal process and acting on the advice of the government of the day, appointed former prime minister Morrison to administer portfolios other than the Department of the Prime Minister and Cabinet," they said.
"It is not uncommon for ministers to be appointed to administer departments other than their portfolio responsibility.
"These appointments do not require a swearing-in ceremony - the Governor-General signs an administrative instrument on the advice of the prime minister.
"Questions around appointments of this nature are a matter for the government of the day and the Department of the Prime Minister and Cabinet.
"Similarly, the decision whether to publicise appointments to administer additional portfolios is a matter for the government of the day."
Anne Twomey, constitutional law expert at the University of Sydney, said it was not unusual for ministers to share responsibility for a single portfolio.
Professor Twomey said, while the secrecy was highly unusual, ministers sharing portfolios typically coordinated to avoid inconsistencies.
She said it could become "seriously weird" if a minister was unaware another minister existed, potentially creating conflicting advice.
"Greg Hunt could have said Australians are not allowed to leave the country, and the prime minister could have put out [a statement] saying that they are," he said.
"They'd be in conflict, and then how do you deal with that? It would have been a complete mess, [and] that would have been the more problematic outcome."
Ministerial power sharing arrangements normally had a set hierarchy, with one deferring to the other, she said.
"Who knows what position the prime minister was supposed to be given in all of this?" she asked.
Given there was no suggestion of illegality, Professor Twomey said the Governor-General had "not a lot of options" to refuse the appointments.
"It may well be that the Governor-General wasn't even aware that it was going to be kept secret," she said.
"And even if he was told that it was going to be kept secret, there's no issue with the legality. He wouldn't have had any right to refuse."
Professor Twomey said there was "increasingly less" adherence to conventions of transparency which underpinned democracies across the globe.
"There [is] a growing disrespect for parliament, openness and transparency ... [and] a growing view that the executive once in power can do whatever it likes," she said.
Kim Rubenstein - professor at the University of Canberra's Faculty of Business, Government and Law - said spreading responsibility for powerful departments was a "healthier way of thinking".
"There is a positive from public attention to this, even though it's in a negative context," she said.
"We should actually be thinking about having more than one person being responsible for a ministry, and having mechanisms in our system of collective responsibility or decision-making where there might be some dispute between two people."
But Professor Rubenstein, who ran for Senator of the ACT on a platform of public integrity, said there were "considerable concerns" over how tightly-held the power sharing arrangement was.
Voters needed to be informed to make judgements on election day, she said. Backbenchers, who were unaware of the arrangement, also needed transparency to hold their leader accountable.
Mr Morrison could have requested the Governor-General assign powers if then-Health Minister Greg Hunt was struck down by COVID-19, and make that decision public, she said.
"It keeps coming back to that transparency and public accountability," she said.
"Our system of ministerial responsibility has been diluted over time.
"This is an expression of the culture that enabled those individuals to think that that was appropriate or acceptable, without more scrutiny or without more public accountability."
George Williams, constitutional law expert at the University of New South Wales, said the matter was unlikely to be a "legal issue" now that the Governor-General had confirmed the appointments were made under Section 64.
Professor Williams said the "key question" was whether the secrecy was wise, saying the public had a right to know, and parliament was unable to function responsibly without full information.
He said the presence of two ministers created huge legal uncertainty over who wielded final authority.
"It hasn't happened [in this case], but they have the potential to contradict each other," he said.
"Maybe the last in time would have the final say, but it would be a mess. It's exactly why you wouldn't do something like this in the first place. You might have a backup or something like that, but it's unwise to do it and it just throws open the possibility of legal uncertainty."
Mr Albanese earlier accused Mr Morrison of having "contempt" for Australian democracy by running roughshod over cabinet, saying his "tin-pot" system would be mocked if it occurred in a non-democracy.
Mr Morrison was reportedly sworn-in to a host of portfolios - including health, finance, and resources - in secret during the last term of government.
Documents obtained by The Australian showed Mr Morrison was sworn-in to control the entire Department of Industry, Science, Energy and Resources by Governor-General David Hurley in April last year.
It followed a new book focusing on Mr Morrison's handling of the COVID-19 pandemic, Plagued, claiming the then-prime minister also had himself secretly sworn-in as co-health and finance minister.
Mr Albanese confirmed he will receive a "full briefing" from Department of Prime Minister & Cabinet secretary Glyn Davis on Monday afternoon, saying new reports were "dripping out like a tap".
"This is extraordinary and unprecedented," he said.
"Let's be very clear: Australians knew during the election campaign that I was running a shadow ministry.
"What they didn't know was that Scott Morrison was running a shadow government. A shadow government that was operating in the shadows."
Mr Morrison claimed he was not aware of his successor's criticisms.
"[I] haven't seen what he has said. Since leaving the job I haven't engaged in any day to day politics," he told Sky News.
Mr Albanese said the swearing-ins undermined cabinet government, but insisted he would not "preempt" legal advice over whether there should be a probe into the matter.
"In Australia, we have a Westminster system of government that produces accountability. This is the sort of tin-pot activity that we would ridicule if it was in a non-democratic country," he said.
"This is a shambles, and it needs clearing up. The Australian people deserve better than this contempt for democratic processes and for our Westminster system of government, which is what we have seen trashed by the Morrison Government."
He demanded current Coalition frontbenchers, including leader Peter Dutton, come clean on what they knew at the time, describing the secrecy as "cynical" and "weird".
Mr Dutton said he was not aware Mr Morrison had controlled multiple ministries.
But Mr Dutton defended his former leader, who he said was weighing the "most confronting period" he had faced in parliament, and "had his reasons".
"This was at the time when there was no vaccine, people were also [making] all sorts of Armageddon scenarios and the briefings were pretty confronting when we first got them in NSC," he told the ABC.
"No doubt all that fit into his logic, but I wasn't part of that. That decision-making process, like in any government, [is] within the domain of the prime minister of the day."
Asked whether Mr Morrison had assumed control of his Defence portfolio, Mr Dutton said: "Not to my knowledge".
Mr Morrison reportedly used the position to scuttle the controversial Pep11 gas drilling project off the NSW Coast, as Liberals faced a wipeout in blue-ribbon inner-city seats, where climate-focused teal independents were launching a strong challenge.
The gas project was supported by then-resources minister Keith Pitt. Former Nationals leader Barnaby Joyce told news.com.au Mr Pitt was "shocked" by Mr Morrison's intervention.
Mr Morrison did not respond to requests for comment from The Canberra Times.
Then-Nationals leader Barnaby Joyce on Monday morning appeared to confirm the swearing-ins, which his successor David Littleproud has described as "pretty ordinary".
Nationals leader David Littleproud, a frontbencher during Mr Morrison's premiership, insisted he was not aware the former prime minister had taken the extraordinary step.
Senior Nationals figures have blasted the development, which leader David Littleproud described as "pretty ordinary".
Nationals frontbencher Bridget McKenzie said the revelations raised "a lot of questions" which needed answers.
"What implications does that have for decisions that ministers made in their capacity with that authority?" she told the ABC.
"This isn't okay."
"This is the sort of tin-pot activity that we would ridicule if it was in a non-democratic country," he said."It was cynical and it was just weird that this has occurred."
"That's pretty ordinary as far as I am concerned," he told ABC RN Breakfast."If you have a cabinet government, you trust your cabinet."
"I don't believe in a presidential form of government," he said to News.com.au"If you don't like cabinet ministers, there's a simple solution: you sack them."
"It's apparent that no one thinks that this is acceptable. You cannot govern Australia in this secretive way," Mr Dreyfus told 6PR.
"I'm sure there will be plenty of commentary about who said what and when, but I focus on what it is that I do, the decisions that I've made, and I stand by all those 100 per cent," he said on Sky News.
"You see now, we had to stop him from swearing himself in as Australian of the Year for 2022," she posted to Twitter.
"Since leaving the job I haven't engaged in any day to day politics," he told Sky News
"I think Prime Minister Albanese has made the right call," Senator McKenzie told ABC. "I always back accountability and transparency."
"We discover that we had a Prime Minister who was acting more from the Donald Trump playbook than the Westminster democracy playbook," Mr Shorten said on ABC Afternoon Briefings.
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