Royal commission lawyers have accused National Australia Bank of having a disregard for the law while questioning if regulators are up to the job of protecting Australians' retirement savings.

NAB and the Commonwealth Bank may have committed civil - and possibly criminal - offences, barristers assisting the banking royal commission say.

They said NAB's superannuation trustees MLC and NULIS may have engaged in misconduct and breaches of corporate and superannuation laws by charging customers fees when no advice service was provided.

NAB was not full and frank with the Australian Securities and Investments Commission about the amount of expected fees-for-no-service remediation, counsel assisting said in outlining conduct falling below community standards.

Senior NAB executive Andrew Hagger told the royal commission the bank was open and transparent with ASIC despite it only hinting at the true scale of compensation.

But counsel assisting said Mr Hagger's evidence that he "left the door open" for ASIC to ask questions revealed "both a disrespect for the role of the regulator and a disregard for the gravity of the events in question".

The closing submission released on Friday night criticised the bank's behaviour over the last few years over fees for no service.

"Assessed as a whole, it is submitted that this behaviour indicates a disregard on the part of the NAB Group for members of the relevant superannuation funds, for regulators and for the law."

ASIC is already investigating "suspected offending" by the NAB group over fees for no service.

ASIC and counsel assisting have accused the bank and its super trustees of failing to report significant breaches of their licence and obligations on time, which is a criminal offence.

The submission also criticised ASIC and the Australian Prudential Regulation Authority over their handling of superannuation issues.

The case studies suggested APRA and ASIC's approach to regulation of superannuation entities is not sufficient to achieve specific or general deterrence, it said.

Counsel assisting said the evidence suggested APRA was reluctant to commence court proceedings and take public enforcement action, adding its approach to dealing with the "intransigence" of wealth manager IOOF could not be considered to be effective.

They said examples of ASIC's approach - over fees for no service and the way three big banks sold superannuation products - raised questions about whether it has struggled to act as an effective conduct regulator.

The royal commission heard CBA tried to convince the regulator to issue a media release rather than take stronger action over the sale of super products in bank branches.

Counsel assisting said it might be thought Australia's largest listed company's dealings with the regulator "suggests the collapse of ASIC's regulatory authority".

They outlined possible misconduct by CBA, although APRA has already decided not to take enforcement action against Colonial First State over 13,000 potentially criminal superannuation offences for failing to move customers to low-fee MySuper products.

The submission also detailed potential misconduct by CBA subsidiary Avanteos over charging advice fees to dead customers' estates.