ASIC chairman Greg Medcraft says addressing culture and conduct at Australia's big banks will remain unfinished business when his term ends in November.

The corporate regulator took aim at the nation's four major banks on Tuesday, saying they were very powerful with "a lot of hubris" and were "not used to being taken on" by regulators.

Mr Medcraft, who was speaking at a Reuters event in Sydney, said he was "not scared of anybody" as he emphasised the need for bigger penalties for white-collar criminals.

A 2014 Senate inquiry stated that ASIC was perceived to be "timid" and "hesitant". It was also seen as weaker compared with Western regulators in terms of the small fines it levied and other penalties it imposed.