The big four banks in Northern Ireland are to face the ultimate sanction of a probe by the Competition Commission over their treatment of customers.
Which? said the NI banks paid "paltry" interest
The unprecedented move by the Office of Fair Trading follows the successful submission of a "super-complaint" by Which? and the Consumer Council.
The banks are the Bank Of Ireland, First Trust, Northern and Ulster banks.
Consumer Council chief executive Eleanor Gill said they had done little or nothing to avoid being in the dock.
"The big four will now be forced to change," she said.
"This referral to the CC brings us one step closer to a fair deal for the hundreds of thousands of local people who bank with the big four.
"They must now remove all charges and give consumers a fair return on their hard-earned money."
Once a reference has been made to the Competition Commission they can take statements from any witnesses, including third parties.
Requests for statements are compulsory and an organisation must respond.
The commission can obtain information (such as profitability data) that the Office of Fair Trading does not have power to demand in the course of its study.
It can also force companies to change the structure of the market in which they operate if it feels competition is being hindered. The OFT does not have this power.
Office of Fair Trading chairman Sir John Vickers said: "Our analysis of the evidence presented to date gives us reasonable grounds to suspect that there are features of this market which restrict competition.
"It is now for the Competition Commission to undertake a thorough investigation of the market and, if necessary, to put appropriate remedies in place."
Bank of Ireland said it believed that "Northern Ireland is an extremely competitive marketplace for financial services".
First Trust said it hoped "this process will now clear up much of the confusion that has been created around this issue".
Ulster Bank said it looked forward to participating in the commission's study of the Northern Ireland market.
The Northern Bank said it refuted any suggestion of price collusion, adding: "We compete aggressively with all players in the marketplace and will continue to do so."