The Financial Services Ombudsman has told RTÉ "it is a source of frustration" to his office that some banks contest hundreds of identical individual complaints through his office.

Bill Prasifka told RTÉ's This Week that banks "should learn from their engagement with us [his office]" and use previous rulings in dealing with complaints in their initial stages.

Mr Prasifka was responding to a Dublin-based financial adviser who is currently representing hundreds of clients who were moved off tracker mortgage rates after a period on a fixed rate.

Padraic Kissane said banks "feel they have nothing to lose" by going to the Ombudsman with individual complaints as the rate of such complaints being upheld by the Ombudsman was low.

Mr Kissane also said that rulings differed in identical cases he had brought to the Ombudsman, which he described as "inconsistent".

Mr Prasifka said thousands of cases come before the Financial Services Ombudsman every year: "I cannot put my hand on my heart and say every one [decision] is perfectly consistent, but we put a lot of work into it.

"We are always trying to improve our decision making. Anyone with a concern about that is free to come and talk to us".

Mr Prasifka also said he expected that the amount of identical complaints being brought to his office would fall in the first quarter of 2014 when his office would be naming banks against whom more than three complaints are upheld.