Thousands of Bank of Ireland customers with ATM-only cards will no longer be able to take out cash from AIB machines.
A large proportion of those affected will be second-level students who have Bank of Ireland cards which they cannot use in shops or online but can use in ATMs to access savings or money lodged by parents.
It follows AIB's move to begin processing financial card transactions through international schemes.
As Bank of Ireland ATM-only cards are not internationally branded, they won't work through the foreign clearing houses, AIB say.
Industry sources say the AIB move was prompted by its decision to replace all its Maestro- branded debt cards with Visa Debit cards – a process which began last year and is now nearly complete.
Bank of Ireland say only a small volume of customers are affected – mostly second-level students.
"However, we have a very extensive ATM network and they also continue to have access to any other ATM provider, with the exception of AIB devices," the bank said.
It added that Bank of Ireland debit cards were not affected.
AIB told the Irish Independent: "AIB is streamlining its processes and routing all transactions through international schemes for processing. As the Bank of Ireland ATM-only card is not an internationally branded card, it will unfortunately no longer work at our ATMs.
"All Bank of Ireland and other banks' debits cards that are internationally branded debit cards will continue to operate at our ATMs as normal."
The number of ATM machines in Ireland continues to fall from a high of 3,404 machines in 2008 to 3,061 in 2012.
That's due to the greater volume of people using "all-in-one" debit cards which they can use at ATMs as well in shops, pubs, restaurants and for other services, as well as online.
There are now one million debit and credit card transactions a day in Ireland.
While the number of traditional credit card transactions have reduced slightly, the number of debit card transactions increased by 8pc in 2012.
Cash withdrawals from ATMs totalled €166.6m in 2012, according to the Irish Payment Services organisation.
On average, Irish people each withdrew €4,375 in cash from ATMs in 2012. That's far lower than the €6,474 per customer six years ago but still 66pc higher than the European average.