NatWest opened around 1000 branches one hour early Friday morning in a bid to placate millions of customers unable to access online services for a second day running.
NatWest, Ulster Bank and their parent RBS were struck by technical problems yesterday when an IT systems glitch failed to properly update customers' balances overnight, leaving many unable to carry out transactions.
This morning the bank revealed that the same problem struck again last night, saying: "Unfortunately we are once again experiencing technical issues with our systems and account balances have not updated properly overnight. This means where money has gone into a customers account, there may be a delay in it appearing on their balance."
The problem is understood to have arisen after staff tried to install a software update on RBS's payment processing system, but ended up corrupting it.
Having kept around 1000 branches open an hour late last night, NatWest opened up early, at 08.00 Friday morning in a bid to calm customers who have become increasingly irate on social networks such as Twitter.
The bank says it recognises that "this is an unacceptable inconvenience for our customers, for which we apologise" but has not provided any hint on when the glitch will be fixed.
With still no sign of a fix by Friday lunchtime, NatWest has vowed on Twitter to extend branch opening again.