The Financial Services Ombudsman dealt with 8,135 complaints last year - the highest number since the office was established in 2005.
There was a 216% increase in the number of payment protection insurance complaints, whilst banking complaints increased by 15%.
The office issued 2,990 findings in 2012 and more than €1.7m in compensation was awarded.
The Financial Services Ombudsman William Prasifka has said the increase in complaint trends in 2012 is of great concern and his office remains at the centre of dealing with legacy issues arising out of the financial crisis.