Finance Minister Mathias Cormann has called on National Australia Bank and its former chairman, Ken Henry, to immediately respond to revelations they knew some of the bank's financial products were ripping off customers.

Senator Cormann said all those involved should "explain themselves" following reports in The Age and The Sydney Morning Herald based on leaked documents, including minutes of meetings held between NAB directors and executives and their auditing firm EY.

Dr Henry, the then NAB chairman, privately told consultants in the midst of the Hayne royal commission he was "confident" the bank was selling products that ripped off its customers and would eventually trigger compensation.

"All those who were involved should explain themselves as part of restoring confidence," Senator Cormann said on Friday morning.