The Financial Services Ombudsman has said his office received almost 7,300 complaints during 2011, with almost half related to the insurance sector.
Bill Prasifka said the number of complaints had levelled off after a number of years of record increases, but added that the level remained high.
He said this showed the continued pressures faced by consumers, particularly in mortgages.
Over 40% of complaints against banks were linked to mortgages, while more than a fifth of insurance complaints were about payment protection or mortgage protection policies.
The Ombudsman also reported a 6% increase in complaints about investment products in the second half of 2011.
As a result of findings by the Ombudsman, €1m was awarded to consumers in the period from July to December, though the percentage of complaints upheld has fallen slightly.
Mr Prasifka said recent trends indicated that financial firms were taking on board his office’s calls to actively engage with consumers about complaints.