Former deputy prime minister Barnaby Joyce insists he was never told the full extent of the then prime minister's new secret ministerial powers.

Scott Morrison appointed himself to administer five departments between 2020 and 2021, which gave him the option to make decisions and override ministers if he saw fit.

Mr Morrison used his new secret powers to ban the PEP-11 gas permit off the New South Wales coast instead of allowing resources minister and Nationals MP Keith Pitt to make the final call.

Barnaby Joyce on Sunday confirmed that while he was in cabinet as Nationals leader, Mr Morrison didn't divulge all the details of the arrangement to him.

"Over a period of time and discussions of the PEP-11 [it] became more apparent that the prime minister had greater powers than I had initially assumed," he told the ABC's Insiders.

"The discussion that I had with the prime minister was purely around the PEP-11. He never went into that he had powers on everything that Keith Pitt could do.

"He never said to me 'I was the minister for resources', he never said that to me."

Mr Joyce also noted that Mr Morrison was sworn into the resources portfolio in April of 2021, when Michael McCormack was leader of the Nationals, and Mr Joyce didn't regain the leadership position until June, when it was too late to intervene.

"Most of it I didn't know about," he said.

"I found out about it subsequently."

Political or national interest decision

The then resources minister, Keith Pitt, was in favour of the PEP-11 gas permit being approved, but at the time it faced large opposition which caused electoral issues for the Liberal Party in marginal seats along the coast.

On Wednesday, Scott Morrison said he did not regret making the final call on PEP-11 and insisted it was in the national interest.

"I don't think anyone who went surfing off the New South Wales coast this week up around Newcastle or the Central Coast would take any issue with a prime minister who lived up to his word and considered this matter from first principles, as I was required to do under the act, which I did without prejudice," he said at a press conference.

Mr Joyce refused to say if he believed the decision had been a political one or if it was made in the national interest.

"That is a question for the prime minister [Mr Morrison] … that's a discussion you can have with them [the Liberal Party]," he said.

Mr Joyce also defended not intervening in the matter as he believed it could have caused the Nationals trouble.

"I had negotiated an extra minister we were not entitled to … I had negotiated extra staff for the National Party which we were not entitled to," he said.

He said Mr Morrison would have taken away a portfolio if he questioned the matter.

"I was absolutely certain that would have happened," he said.

"I have been in politics about 18 years, I know how it works."

Albanese indicates possible investigation

The current Prime Minister, Anthony Albanese, has asked the solicitor-general to examine whether any laws were broken, and that advice will be provided to him on Monday.

Mr Albanese has also indicated an inquiry could be launched into the former prime minister's decision to secretly take on the five ministerial roles, to ensure there is proper scrutiny of what occurred.

"I haven't seen yet a suggestion that anything illegal has happened but what is very clear is that conventions have been overturned completely and ignored, and the Westminster system of our democracy has been undermined by the decisions that were made by the former prime minister," he told Sky News.

"I'm not going to pre-empt the advice (from the Solicitor-General) that we receive, but very clearly there's a need for proper scrutiny of what occurred here.

"This was an undermining of our parliamentary democracy, and what the Solicitor-General will advise on is of course the legal issues."

Mr Morrison argued that one of the reasons he took on the secret additional powers was to ensure he could step into a role if a minister caught COVID-19 and couldn't work.

However the Westminster system allows for acting ministers to be appointed immediately.

Mr Albanese has suggested that if an inquiry were to be launched, it would look at whether reforms were needed to ensure such moves by a leader could not be made again.

"There's separate questions about the functioning of our democracy, about conventions and whether any conventions have been overturned, and whether there's a need for any reforms required to ensure that something like this can never happen again," he said.

"We'll examine all of those issues after we receive the Solicitor-General's advice."