Analysts have given the thumbs ups to the resignations of NAB chief executive Andrew Thorburn and chairman Dr Ken Henry and the appointment of Phil Chronican as acting CEO however investors appeared less sure with shares sold off against a broader rally in bank stocks.

More than two million shares in NAB had changed hands in the opening half hour of trade or more than double the shares traded of any big four bank stock. NAB shares dipped, rallied and then weakened by 11.30am shedding 70c or 0.3 per cent to $28.86.