A Commonwealth Bank spokesperson said:

"We have advised the Finance Sector Union (FSU) that we take their concerns very seriously and that we are committed to complying with obligations.

"We are currently investigating their concerns and we have made it clear to them that, if following investigations we identify any issues, we will rectify them.

"We understand the importance of superannuation to help secure and enhance the financial wellbeing of our employees, and we are committed to ensuring we comply with obligations to employees."