ULSTER bank have this morning apologised to their customers after they were left unable to withdraw funds from ATM machines or access their accounts online last night.
This is the second time in the past nine months customers have been locked out of their funds due to technical errors.
Royal Bank of Scotland, the owners of Ulster Bank, apologised to its millions of customers about the inconvenience on Twitter at 11.30pm. The problem was later resolved at around 1am.
A spokeswoman for RBS said: "We are disappointed that our customers have faced disruption to banking services for a period this evening, and apologise for that. All services are now running as normal again."
She added that any customers having continued difficulties should contact customer services.
RBS was unable to give details about why the service was affected and whether it stopped payments and direct debits being paid.
Customers complained on social media site Twitter about being unable to access their money. Charlie O'Brien tweeted: "Yep my card just got declined. Not able to use cash points or online banking #natwest not good at all ....."
She later added: "I had to get my info from twitter! No details anywhere else about whole system being down. Poor show."
Stephen Hester, the chief executive of RBS, which is 80% state-owned, was forced to apologise last June after millions of customers were left unable to view an up-to-date balance following a software update. It also affected payments such as direct debits for bills and some wages were not received.
The Consumers' Association of Ireland today said the glitch raises serious concerns for customers.
CAI chief executive Dermott Jewell said: "It affected quite a significant number of people yesterday who needed to access the system to download money, to take care of their banking needs and they couldn't.
"And realistically it needs to be borne in mind that they're paying for this service and it's just not up to scratch.
"If we hark back to June there, the lessons from then do not seem to have been made clear to the customers of Ulster Bank to explain what has happened, what has been put in place to make sure there's a system that's robust."