Senior executives within ANZ's institutional bank, including the former managing director, all resigned at around the same time the bank was subject to an investigation by the corporate watchdog over the alleged rigging of the bank bill swap rate.

The revelation came as ANZ also defended its treatment of small business customers, particularly farmers, to the parliamentary committee running the ongoing inquiry into the banking sector.

ANZ chief executive Shayne Elliott confirmed on Tuesday to the committee the executives had all let the bank "at around the same time".

The executives named before Parliament today by Labor MP Matt Keogh were former global head of markets Steve Bellotti, former acting managing director of markets Eddie Listorti, former head of global markets sales Peter Maddox and former head of ANZ's institutional bank Andrew Geczy.