Senator O'Sullivan is relying on two lower house colleagues to cross the floor to supply the absolute majority of 76 votes needed to bring on the bill for debate and ensure its passage, possibly before Christmas.

A commission of inquiry is effectively the same as a royal commission but is established by the Parliament, rather than the executive, and will report to the Parliament, not the executive. The Parliament sets the terms of reference and chooses the commissioner.

Senator O'Sullivan got the idea after moderate Liberals conceived a private members bill with cross-party sponsorship as a way to legislate for same-sex marriage. This sidelined conservative hardliners who wanted to bog it down with protections for religious freedoms.

Senator O'Sullivan argued if the moderate Liberals were able to use such a mechanism, then so could he.

But Mr Howard called for restraint.

"I would say to my former colleagues and people I still support, don't embrace a royal commission and to those in the National Party and elsewhere who might see this as some kind of retaliation for cooperation between people on the same-sex marriage issue, I would say 'I agree with those people in the National Party on the substance of the same-sex marriage issue, but that is over.'," he said.

"Let's not visit upon the Coalition and the fortunes of the government your anger and disappointment about that issue."


The bank revolt is just one issue currently destabilising the government. There is also finger pointing going on as to who leaked a cabinet discussion in which ministers canvassed raising the white flag and having a royal commission so it could be controlled. Eventually, it was agreed to hold the line.

Senior conservative Peter Dutton, who according to the leak was open to a pragmatic approach, railed against the cabinet leaks.

"I'm not going to comment on any Cabinet matters, but if people are leaking then they don't do anybody any good. There's no good that comes of it. And as I've said, for a long time, I mean I've served under four Liberal leaders now. I've served each of them, starting with John Howard, loyally, and I continue to do that to this day," he said.

"I offer my frank advice, I argue with the Prime Minister, he argues with me behind the scenes about different policies or decisions that the Government might make. I support him 100 per cent because I believe Bill Shorten would be a disaster for this country.

"Prime Ministers want frank advice and I give frank advice and we work to get the best possible outcome. And if people believe that somehow their careers are furthered by leaking or by trying to put out something that's going to damage the Government, or damage me, or damage Malcolm, well, look it says more about them than it does about us."

Nationals frontbencher Keith Pitt defended his colleague's right to push for a commission in the banks, saying the Nationals had supported the approach for a long time.

Nationals leader Barnaby Joyce has asked Senator O'Sullivan to reconsider and is believed to be pressing LNP MP George Christensen not to cross the floor in the lower house.

But Mr Pitt noted Mr Joyce himself was a renegade in his back bench days.


"We're led by Barnaby Joyce who crossed the floor more than 20 times," Mr Pitt said.

"I don't think it is different at all."

Treasurer Scott Morrison, who opposes any commission, plans to raise the issue with scheduled meetings with bank bosses, urging them to help the government ward off calls for an inquiry.

On Thursday he was due to meet NAB chairman Ken Henry and Westpac chairman Lindsay Maxsted

"I meet with the banks on a regular basis. That's one of my responsibilities as Treasurer and I do so in particular with the chairs. I speak to the CEOs and executives as you would expect me to do," Mr Morrison said.

"I'll be having further discussions with a number of them today. For some years now I've been talking to the banks about resolving some legacy cases where people have had issues.

"These cases have been raised in various fora. I've been impressing upon them for some time now the need for those cases to be resolved and, like in other meetings I've had with them, I'll continue to have those discussions as well as on other matters."