Agriculture Minister Barnaby Joyce's angry outburst against the government's approval of a massive Chinese-owned coal mine may have breached strict protocols for ministerial behaviour and cabinet solidarity.
The updated 2015 cabinet handbook says ministers must not "express private views on Government policies nor speak about or otherwise become involved in a ministerial colleague's portfolio without first consulting that colleague and possibly the Prime Minister".
The handbook also lists protocols for cabinet solidarity. "Cabinet ministers cannot dissociate themselves from, or repudiate the decisions of their Cabinet colleagues unless they resign from the Cabinet," it says.
Mr Joyce this week greeted the approval of the mine in the heart of the fertile Liverpool Plains in his New England electorate with the memorable – and damaging – phrase "the world has gone mad".
A spokesman for Mr Joyce said the rule about quitting cabinet did not apply because it was not a cabinet decision he was criticising, rather a ministerial decision based on advice by independent scientific experts.
The handbook states: "The Cabinet principles and conventions apply to the whole Ministry, not simply those ministers in Cabinet."
In 2009, Mr Joyce told the ABC he would "hold his tongue" rather than criticise shadow cabinet colleagues. "And if I can't I'll have to resign from cabinet and I don't intend to do that because it would make the place look like a farce," he said at the time.
On Friday, Mr Joyce ruled out resigning from cabinet over the decision to allow the open-cut mine.
Labor's agriculture spokesman, Joel Fitzgibbon, said the deputy Nationals leader needed to "consider his position on the frontbench" following the outburst.
Mr Joyce stepped up his criticism on Friday and even contradicted Prime Minister Tony Abbott's assertion that he was speaking out against it in his capacity as as local member rather than as a minister.
"You can do a lot of things as a local member," Mr Abbott said. "Local members are required from time to time to give voice to the feelings of their constituents, that's what local members do."
The leader of the government in the Senate, Senator Eric Abetz, last week said cabinet members who had publicly declared their support for gay marriage – against the party's formal position on the issue – should resign.
Pressed about whether his criticism of the mine approval breached cabinet solidarity rules, Mr Joyce said: "I don't think [resigning] would achieve anything."
Mr Abbott declined to be drawn on Friday on whether Mr Joyce should be disciplined or resign from cabinet over his comments, saying only that he was "expressing some disappointment" over the government's approval.
Asked whether he had told Mr Joyce to "pull his head in", Mr Abbott said: "I've had a lot of conversations with all my ministers, that's what a good prime minister does."
Mr Joyce pulled out of an expected appearance with Mr Abbott in Grafton on Thursday, with both citing scheduling difficulties.
Mr Joyce denied suggestions he was publicly opposing the mine to shore up support in his electorate.
"I never agreed with this mine from the start," he said. "I've been quite open about that. I think everything I've said on the public record is that I don't agree with it."
Former independent MP Tony Windsor has said he is considering challenging for Mr Joyce's seat of New England in light of the mine's conditional approval.
Mr Joyce has written to NSW Premier Mike Baird, who has the final power to approve the mine.
