ASB says it has uncovered a serious case of fraud by a bank employee who provided investment advice to customers involving several million dollars.
The bank says the fraud involves 22 customers, all of whom have been identified.
It says it has made restitution to customers where irregularities have been confirmed and is continuing to work with them to ensure no customer is adversely affected.
The employee, who worked for ASB for more than 10 years, has been dismissed and is being investigated by the Serious Fraud Office.
The bank says the employee acted alone.