Queensland LNP senator Barry O'Sullivan says he is drafting a bill to force a powerful Commission of Inquiry into the banking and financial services sector, warning Prime Minister Malcolm Turnbull there are four MPs in the House of Representatives who are prepared to cross the floor.
The government does not support a commission into the banks, which has long been advocated by Labor and the Greens.
But Senator O'Sullivan said he was now drafting a private member's bill to trigger the inquiry.
He said Senator Dean Smith's bill to legalise same-sex marriage demonstrated a "new pathway for backbenchers to pursue matters of importance to them".
"Millions and millions of Australians have been affected by the behaviour of the banks over time," Senator O'Sullivan said.
"They show an almost autistic disregard for prudential regulation and law, and it's time for these people to have their day in court."
The senator said there were "as many as four" Coalition MPs in the Lower House who would cross the floor and vote for the bill, and said he would have a draft bill ready as soon as Wednesday.
He said millions of Australians had been affected by banks which should be forced to answer to the inquiry.
"If both houses of the parliament think this a good thing to do and that is the decision, I think the prime minister has to sit up and take note of that," Senator O'Sullivan said.
Mr Turnbull has long resisted calls for a Royal Commission or a similar Commission of Inquiry into the banking sector.
Trade minister Steve Ciobo rejected the renewed push, arguing the government has already taken more immediate action.
"We've given more money and more teeth to the banking regulators, in particular to both ASIC and to APRA," Mr Ciobo told ABC Radio.
Resources minister Matt Canavan said a commission would be a waste of time that would "turn into a bit of a lawyers' picnic".
Australian Bankers Association chief executive Anna Bligh said the inquiry was an extraordinary and unnecessary step which could cost taxpayers up to $53 million.
"The justification that's being used publicly for these actions by this group of senators are seeking revenge for the fact they didn't get their way in the same-sex marriage debate," she told ABC radio.
Senator O'Sullivan will introduce the bill to the Senate once the same-sex marriage bill had been dealt with, making it likely to hit parliament before the end of the year.
"If it fails, it fails but if it passes it'll give the government a chance to be able to put things in place so that we could have this Commission of Inquiry commencing early in the new year," he said.
- with AAP
