Nationals Senator, Barry O'Sullivan, has said last week's private members bill on marriage equality set a precedent that would allow him to put a banking bill to parliament.

With Barnaby Joyce absent until the New England by-election and speculation the Liberal's John Alexander might not be able to hold Bennelong against Kristina Keneally it would stand a better than even chance of getting up.

Both the ALP and The Greens have voted in favour of similar proposals in the past. Mr O'Sullivan and Nationals Senator, George Christensen, have said they would cross the floor. Mr O'Sullivan also said at least two or three other Liberal and National Party MPs and Senators would follow them.

While this would be a serious embarrassment for the Turnbull Government, which has rejected all calls for a Royal Commission or Commission of Inquiry in the past, it would likely be well received by voters long dissatisfied with the big four banks.

There is a widespread belief that while they have been delighted to have their deposits guaranteed by taxpayers since the height of the global financial crisis in 2008 the megacorporations have given little or nothing back in return. If anything the reverse has been the case.

Interest rate cuts have taken an inexplicable length of time to pass on even though rises are applied to home loans almost immediately; home loan rates have increased even when the Reserve Bank has held its rate steady and credit card interest rates are at punitive levels.

Given fees for services such as, until very recently, inter bank ATM cash withdrawals; loan establishment fees; account keeping fees and the like are usually far higher than the cost of providing them, it is no surprise Australia's banks are the most profitable in the world.

Public resentment against what is seen as an inordinate focus on profits at the expense of the customer is strongest amongst those old enough to remember the largest of the big four, The Commonwealth, was originally established by the Federal Government and owned by the taxpayers.

With the days when local bank branches focused on customer service rather than up-selling account holders into financial services of often dubious value and utility now long gone, the sector's community standing is at a low point.

A string of scandals spanning many years, including one that saw the NAB sack 20 staffers for malpractice in recent weeks, prosecutions for manipulating bank bill prices, the $360 million NAB currency options trading scandal, the CommInsure debacle and the collapses of Opes Prime, Storm Financial and Allco and Babcock and Brown have all played their part.

If and when Senator O'Sullivan, Bill Shorten or Richard Di Natale do get their Royal Commission or Commission of Inquiry the banks will have nobody to blame but themselves.