Amid mounting speculation the criticism could cost Mr Thorburn his job, the CEO this week dug in, insisting the bank had not been dishonest in a scandal that saw NAB collect $100 million in fees without providing service in return.

Mr Thorburn cancelled plans to take long service leave to deal with the fallout from the royal commission, and on Tuesday said he had the full support of the board.

Separately, Sydney Morning Herald and The Age reports on Thursday into suspected large-scale fraud by Mr Thorburn's former chief of staff had insiders describing a culture of largesse and extravagant spending in his office, putting his executive oversight in question.

More to come...