A technical problem has forced banking giant NatWest to extend its opening hours yesterday, as thousands of customers have been affected by account unavailability.
On Thursday afternoon NatWest said in a Twitter message: "We will be keeping over 1,000 NatWest branches in all major towns and cities open until 7pm to assist customers."
NatWest has told Sky News that no customers "would be left out of pocket because of the technical problems we have experienced".
RBS earlier said in a statement: "We are currently experiencing technical issues which mean that a number of customer account balances have not yet been updated and some of our online services are temporarily unavailable.
"We are working hard to fix this and hope to have the problem resolved as soon as possible.
"We apologise for the inconvenience caused to our customers."
The bank problems came amid news that credit ratings agency Moody's would downgrades major world banks, including the RBS group.
The technical issue at RBS and NatWest has also caused problems for customers and staff in local branches.
The NatWest customer service department had earlier tweeted: "This is an unacceptable inconvenience for our customers for which we apologise.
"We are still working hard to fix the current technical issue and hope to resolve within the next few hours. Sincere apologies."
Some customers have contacted Sky News and said that both personal and business accounts, including salary payment systems, were affected by the computer problem.
RBS repaired most account balance information details by late afternoon but acknowledged by Twitter that the issue was "impacting some credits into your accounts".