Bank of Ireland is warning those switching banks over the coming months to watch out for scams.
Hundreds of thousands of current account customers will be moving their accounts, ahead of Ulster Bank and KBC's exit from the market.
Bank of Ireland's fraud team said consumers should expect an increase in scam calls, texts and emails, as fraudsters commonly take advantage of periods of change to target customers.
The bank said consumers should independently verify messages or calls asking for personal information or account details, or containing warnings around the cancellation of important payments.
It said fraudsters will try to introduce a sense of urgency to persuade consumers to give away their banking details.
"We know that periods of major change or uncertainty create ideal conditions for fraudsters to operate," said Edel McDermott, Head of Group Fraud at Bank of Ireland.
"The rise in fraud recorded during Covid 19 and Brexit demonstrates this.
"The number of 'phishing’ websites detected by our Fraud Prevention Team doubled in one month alone in 2021 and, at its peak, we saw 70 new fraudulent sites appearing per day," she added.
Ms McDermott said the current mass movement of customers between banks creates ideal conditions for criminals.
"As customers make arrangements to move their bank accounts and make changes to their direct debits and standing orders, they will be expecting communications from a whole range of providers.
"Protecting our customers against fraud at all times is a top priority," she said.
So far this year, Bank of Ireland said it has opened double the number of personal current accounts compared to the same period last year.