National Australia Bank's CEO says the scandals revealed in a royal commission have been upsetting and damning as banks put profits before people.

Andrew Thorburn said he was wrong to oppose the banking royal commission.

"The royal commission has given us real cases of real customers, where we've made terrible mistakes," Mr Thorburn told the inquiry on Monday.

"When you read the case studies, you say this is so upsetting and so damning, what went wrong?"

But he admitted banks already knew about the cases exposed at the royal commission.

Mr Thorburn said the banks can be criticised for putting profits before people and having focused too much on the short term.

"Focusing too much on growth, short-term growth that's not really sustainable and a sales culture was introduced, not just in our bank, in the system," he said.

"I think that created wrong outcomes as well, unintended consequences."

Mr Thorburn said the banks had to get the basics right, which meant focusing on services and relationships.

"It should not be sales based.

"I think if we don't do that inside our company and in the sector, we will continue to make mistakes and be exposed because it's not really sustainable.

"Now, I'm not saying that, you know, growing your business isn't important but your motivation must be to look after your client. That's the primary objective."

NAB has changed its remuneration for executives to reduce the focus on shorter-term sales incentives.