Royal Bank of Scotland Group Plc, Britain’s biggest taxpayer-owned lender, apologized for a technical fault that left customers unable to access accounts and offered to compensate those who have lost money.

"The system issues that affected our customers last night have now been resolved," Linda Harper, a spokeswoman for RBS, said in an e-mailed statement Dec. 3. "We have heard from some customers who are experiencing issues this morning as systems get back to a fully normal service. We will continue to monitor the service throughout the day and apologize for the inconvenience this has caused."

Some customers at RBS and its Natwest and Ulster Bank units couldn’t withdraw cash or pay for purchases using their debit cards for about three hours. RBS estimates that about 250,000 people an hour use its automated teller machines between 6:30 p.m. and 9:30 p.m., when the glitch occurred. The Edinburgh, Scotland-based bank said if any customer has been left "out of pocket," it will "put this right."

RBS was hit by a computer failure at its consumer bank in June 2012 that left many of its customers unable to access their accounts for days. That prompted the financial regulator to send letters to the U.K.’s nine largest banks and building societies, reminding them of their obligations and urging them to have robust information-technology systems in place.

"Last night’s systems failure was unacceptable," RBS CEO Ross McEwan said in a statement. "For decades, RBS failed to invest properly in its systems. It will take time, but we are investing heavily in building IT systems our customers can rely on."

McEwan, who took over from Stephen Hester in October, has been under pressure to sell assets as Chancellor of the Exchequer George Osborne tries to recoup some of the cost of the bank’s 35.5 billion-pound bailout. The lender said last month that it expects to post a "substantial" full-year loss after transferring 38.3 billion pounds ($63 billion) of its worst loans to an internal bad bank.

The CEO said he’ll present plans in 2014 for "making RBS the bank that our customers and the U.K. need it to be" including details on future investments.

"Since the start of the financial crisis, Royal Bank of Scotland has announced over 30,000 job losses," the Unite labor union said in a statement. "IT problems will do nothing to reassure customers that RBS’ commitment to quality customer service is backed up by proper investment in staff and systems."

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