The royal commission will next week have about five days to grill bankers over their treatment of farming customers, following complaints of aggressive enforcement of some loan contracts.

Deputy Nationals whip Llew O'Brien, who supported internal moves to push for a banking inquiry, said if royal commissioner Kenneth Hayne wanted more time, he would champion that position in the party room.

"It's yet to be seen [whether he needs more time] but if that is the case, that we need more time, we must provide more time," he said. "This is a once-in-a-generation opportunity to get the financial services sector back on track.

"We can't waste this opportunity by not resourcing it properly or not giving them enough time. It's that serious, it's not something that's going to happen again in the near future, so we've got to get it right."

Mr O'Brien said he expected there would be some very sad stories coming out of next week's hearings.

"There's a reason we're having this royal commission and I think the banks have got a lot to answer for, I think, in relation to some of their heavy-handed practices and valuations," he said.

Finance Minister Mathias Cormann has previously said the year-long inquiry would be extended if Mr Hayne requested more time.

NSW Nationals senator John Williams said he realised the commission was on a tight schedule but it needed to spend plenty of time scrutinising the issues.

"Just as it has put the fine tooth comb through the financial planning sector," he said. "This is the one chance to get it right."

This week, the federal member for Dawson, George Christensen, said he supported Small Business Ombudsman Kate Carnell's call to extend the commission's time to investigate small business loans.

Mr Christensen was unable to say yet whether more time was needed for farming finance but said he was aware of allegations of "appalling" treatment of farming families by banks.

"There are situations I've seen where farmers who are in distress, who could be assisted, it's normally due to drought or something like that, are pretty much dealt with brutally," he said.

Senator Barry O'Sullivan, who long agitated for the commission of inquiry from within the Coalition, said it might sound strange, but the frequency of the banks' misbehaviour relating to  farming finance was not on the "scale" some tried to argue.

"I actually think in some instances, the banks did work with clients for a period of time," he said. "But where they did fail, they failed spectacularly."

Senator O'Sullivan said bank decisions could put a "complete fright" into the marketplace, and push down the value of assets in entire regions, giving an area a reputation for "cheap property" it did not deserve.

"Trust me, I'm not trying to make the case the banks don't deserve every single thing that's happening to them now," he said.

Senator O'Sullivan said some features in banks' lending products were potential "landmines" for rural property owners, as they were not flexible enough to deal with climate conditions, such as lengthy droughts.

Witnesses at next week's hearings are expected to include customers of businesses that were taken over by major banks, including Landmark, which ANZ Bank bought from AWB in 2010, and Bankwest, acquired by the Commonwealth Bank at the height of the global financial crisis in 2008.

Groups of Commonwealth Bank and ANZ customers have alleged the big banks acted too hastily in putting many borrowers into default after the takeovers. CBA has denied wrongdoing in relation to Bankwest, while ANZ has admitted to making some mistakes in its dealings with Landmark customers.

On Monday, witnesses will include representatives from Legal Aid Queensland, the Australian Securities and Investments Commission and ANZ. Dutch agricultural bank Rabobank, National Australia Bank, and Bendigo and Adelaide Bank are also set to appear in the Brisbane hearings.

Queensland MP Robbie Katter said he was hopeful the commission would continue to apply the blowtorch to dodgy lenders when it heard from farmers next week.

"I'm also hoping that what comes out of it is they identify that the banking system in agribusiness is inadequate to deal with the nuances of agricultural industries," he said.

with Clancy Yeates