The next chief executive of NAB has a "mountain to climb" to bring the bank into line with community expectations, its outgoing chairman says.
Ken Henry and NAB chief executive Andrew Thorburn resigned from the bank on Thursday, in the aftermath of the financial services royal commission.
Treasurer Josh Frydenberg says he wasn't involved in their decision to resign, but that Dr Henry called him to share the news.
Mr Frydenberg says Australia's banks must now focus on changing their internal cultures and make practical changes within the organisations.
"Kenneth Hayne did provide a very scathing and clinical assessment of the culture and the conduct in our financial institutions," he told ABC radio on Friday.
"Ultimately the responsibility of the misconduct falls at the feet of those senior executives and those board members within the companies."
Commissioner Kenneth Hayne's final report - made public on Monday - expressed serious concerns about the pair's leadership and failings that included charging fees for no service.
"Overall, my fear - that there may be a wide gap between the public face NAB seeks to show and what it does in practice - remains," Commissioner Hayne said.
Dr Henry said he agreed with Mr Hayne that there was a big gap between what NAB aspired to be and what it currently is.
The bank's next chief executive will need to be able to deliver a new culture that delivers good service to customers every time and everywhere, he added.
"We all know we're on the right path, but we're nowhere near the top of the mountain. The CEO that we bring in as Andrew's successor has to take us to the top of the mountain."
Mr Thorburn, who was chief executive since August 2014, took apologised for his role in the bank's failures.
"I'm disappointed about that, I'm sorry for that and I'm accountable for that."
But Opposition Leader Bill Shorten said the resignations would be of little comfort to victims of the banking industry.
"They don't want to just see a couple of bankers kissed goodbye with golden handshakes," he told AAP.
"They want real change to cut the rot out of our banks. This is what the Royal Commission has recommended.
"We must start legislating on these recommendations before the election."
Mr Thorburn will finish at NAB on February 28, while Dr Henry indicated he would retire from the board once a new permanent CEO had been appointed.
Philip Chronican, a current NAB director with extensive domestic banking experience, will serve as acting CEO from March 1 until a permanent appointment is made.
The NAB board will initiate a global search process for the CEO role while actively considering a range of quality internal candidates.
