ISME, the small business lobby group, said it was "extremely concerned but not surprised" that AIB had been "ripping-off" an unidentified number of its customers.
Mr Mark Fielding, the chief executive of ISME, said: "It is ironic that in the week the Irish Bankers Federation have been throwing out spin with regard to Irish bank charges being cheaper than those in the UK one of its main constituent members has admitted overcharging with regard to bank transactions."
He called for IFSRA to undertake an "in-depth investigation into bank charges and the interest rate structure as applies to the public and SMEs".
The Tánaiste, Ms Harney, said the affair underlined the critical role for the Irish Financial Service Regulatory Authority (ISFRA) in providing a strong integrated consumer protection focus in the financial services sector and she expects the matter will now be pursued on the consumers' behalf by the consumer director of IFSRA.
The Fine Gael spokesman on Enterprise, Trade and Employment, Mr Phil Hogan, said: "We have grown wearily accustomed to stories of overcharging across a range of sectors, but for one bank to overcharge its customers by €14 million puts all other stories in the shade."
The Labour spokeswoman on finance, Ms Joan Burton, said: "It appears that despite all the scrutiny to which they have been subjected in recent years some in the financial sector have still refused to learn their lesson and are still prepared to squeeze every possible cent out of their customers by fair means or foul.".
Sinn Féin spokesman on finance, Mr Caoimhghin Ó Caoláin, said: "There needs to be full investigation of these practices and much tighter regulation and control of charges by the State.
