Former deputy prime minister Barnaby Joyce told News Corp that Morrison was sworn in as the second resources minister in December last year.
Morrison then used his ministerial powers to stop controversial gas projects slated for the NSW coast, which teal independent candidates – an increasing election threat – opposed, Joyce said.
The report comes as a new book, Plagued, by Simon Benson and Geoff Chambers, claims Morrison also swore himself into the health and finance portfolios.
David Littleproud, who replaced Joyce as the Nationals leader, told ABC’s RN Breakfast program he did not know about Morrison’s extra ministerial roles.
“That’s pretty ordinary, as far as I’m concerned. If you have a cabinet government, you trust your cabinet,” Littleproud said.
“You create that environment in the cabinet room to have those discussions.
“If you don’t think a minister’s suitable to do that, that’s a discussion with the minister [and you] probably ask him or her to remove themselves.”
Prime Minister Anthony Albanese is seeking legal advice about Morrison’s secret ministerial roles and is expected to address the media this morning on the issue.
Immigration Minister Andrew Giles told ABC Radio that Morrison “ripped up the rule book”.
“This is the most extraordinary development,” he said.