NI's big local banks face investigation by the Competition Commission over allegations they rip off personal customers with high charges.
An Office of Fair Trading report said there was evidence of "weak competition" between the banks.
It follows a "super-complaint" by the consumer association Which? and the NI Consumer Council on bank charges.
The OFT has said it will consult on referring the industry to the Competition Commission.
Northern Ireland's four local banks are the Bank of Ireland, First Trust, Northern Bank, and the Ulster Bank.
In November, Which? lodged the super-complaint with the OFT - it then had 90 days to do a preliminary investigation and decide what action to take.
Sir John Vickers, chairman of the OFT, said: "Our analysis of the super-complaint has identified questions about the effectiveness of competition in the provision of personal current account services in Northern Ireland.
"We will now consult with the banks that would be affected on the case for a reference to the CC for fuller investigation of the market."
He said the consultation would last for five weeks and close on 18 March.
The Northern Bank has already said it plans to drop its fees and charges - but it and the other three banks will now have a further five weeks to try to persuade the OFT not to make the referral.
Which? said the OFT report had "signalled the beginning of the end for the Northern Ireland banking rip-off".
"The market is condemned as being anti-competitive and acting against the consumer interest," said Phil Evans, of Which?
"Putting the Northern Ireland Big Four in front of the Competition Commission will force transparency in an opaque market and highlight real solutions that will cut banking costs for consumers."
On Friday, Bank of Ireland said it "acknowledges the OFT's response and welcomes the opportunity to participate fully in the consultation that will be undertaken".
The Ulster Bank said it "believes that it has a strong case to make and looks forward to participating in the OFT's consultation and it is confident it will be able to allay OFT's concerns."
The Northern Bank said: "We co-operated fully with the OFT in their investigations and welcomed the opportunity to do so."
First Trust Bank said it "has co-operated fully with the OFT throughout its three month review and will now enter into a period of further consultation in order to address the questions raised but not yet resolved by the OFT".