The kingpins of the National Australia Bank board have hit back at damning critiques of their performance from royal commissioner Kenneth Hayne and are vowing to continue in their roles despite mounting pressure to resign.Chief executive Andrew Thorburn yesterday tried to dispel commissioner Hayne's assessment that NAB had not learned lessons from its past mismanagement, including the fees for no service scandal that has cost thousands of advice customers more than A$100 million."The commissioner has expressed his view that we at NAB may not be learning the lessons we need to from the past and, in particular, that we don't know what the right thing to do is," Thorburn told shareholders in an ASX filing."As the CEO, this is a very hard read, and does not reflect who I am or how I am leading, nor the change that is occurring inside our bank."While we have made mistakes, I believe there is a lot of evidence that we are making sustainable and serious change to once again regain the trust of all our customers."The embattled NAB boss revealed that he had cancelled his long service leave in order to lead the bank "with even greater urgency and intensity".In an interview on Melbourne radio station 3AW, Thorburn said he did not know if the bank could face criminal charges arising from evidence heard by the royal commission."We're not aware of that at this point," he said.When asked whether he was concerned that he personally might face a criminal charge, Thorburn said: "There's a long journey to go here to look at the facts and for it to be really assessed properly and in a balanced way."Thorburn was then asked whether NAB had done anything illegal."Well, I think there are some things that we have not done that are breaches of certain regulations," the NAB CEO said."Some of those we are working with the regulator on now."If they're referred to the regulator - new ones - whether maybe criminal charges or not, we'll work through those."Thorburn stuck to his argument presented to the hearings of the royal commission last year that the bank had been "sloppy" in remediating customers affected by the fees for no service scandal.While he said this reflected a poor culture, the bank did not do it deliberately.NAB chairman Ken Henry also responded to commissioner Hayne's charge that he was unable to accept criticism of the board's performance."In his final report, Commissioner Hayne said I seemed unwilling to accept criticism of how the board had dealt with some of the issues raised by the commission," Henry said."I am disappointed that the Commissioner formed this view. I know it is not so."The board and I have reflected deeply on those and other issues and, as I have said previously, we take them very seriously."