The review by the Financial Services Ombudsman shows that the number of complaints about financial institutions continues to rise.
It also shows that the same types of complaints are recurring each year.
Almost 4,700 complaints were made by consumers to the Financial Services Ombudsman between January and June this year, a 27% increase on the same period last year.
Complaints about insurance accounted for half of all complaints received, with Payment Protection Insurance accounting for the majority of all insurance complaints.
Mortgages and accounts generate the most complaints against banks and 10% more complaints are upheld against the banking sector compared to the insurance and investment sectors.
Ombudsman Bill Prasifka said a large number of financial institutions treat his office as just another complaint department.
Recent changes to legislation means the Ombudsman will be able to publish complaint records of individual financial institutions in future reviews.