Complaints to the Financial Services Ombudsman hit their highest level last year since the office was set up in 2005.
Ombudsman Bill Prasifka said the trend of growth in the number of complaints is of great concern.
There were 8,135 complaints lodged with his office in 2012, up 12% on 2011 levels, according to the office's latest bi-annual review.
The second half of the year saw complaints more than double compared to the first six months of the year.
Complaints alleging mis-selling of insurance to credit card and mortgage customers more than trebled to 1,280 last year.
Mis-selling of such products has been a major issue in Britain, leading to billions of pounds in compensation being paid to British consumers.
The Central Bank has been investigating practices in Ireland over the past year.
In all, 2,990 findings were made against various financial institutions by the FSO last year, with €1.7m in compensation awarded.
Mr Prasifka said the complaints trend in 2012 are of great concern.
He said: "While more complaints are being settled on referral to the FSO, it is not in the interest of consumers or financial institutions to see a continued increase in complaints overall.
Mr Prasifka said the reason for the increase in complaints is the fact that the FSO remains at the centre of dealing with legacy issues arising out of the financial crisis.
He said: "For many citizens, their lives can not move forward until these matters are dealt with fairly, effectively and expeditiously."
Mr Prasifka said that while the number of new complaints and complaints in formal investigation remain at record levels, the FSO is committed to dealing with them in a timely manner and within its current resources.