The chief executive of RBS has apologised to NatWest customers as problems resulting from a technical glitch which has affected millions runs into a seventh day.
NatWest has announced it will extend its opening hours again to help deal with the problems after more than 1,000 branches were opened on a Sunday for the first time in the company's history.
The computer failure, which also affected RBS and Ulster Bank, saw payments not appearing in customers' account and meant some were not able to pay bills on time.
Many customers were unable to access their account online because of the glitch. NatWest and RBS have admitted the issues may continue for the rest of the week.
Stephen Hester, chief executive for RBS Group, issued an apology to all those affected by the glitch and admitted the computer failure "should not have happened".
He said: "I am very sorry for the difficulties people are experiencing. Our customers rely on us day in and day out to get things right, and on this occasion we have let them down. This should not have happened.
"Right now, my top priority, and the priority of the entire RBS Group, is to fix these problems and put things right for our customers.
"This is taking time but I want to reassure people that we are working round the clock to resolve these problems as quickly as we are able.
"I also want to reassure customers that no one will be left permanently out of pocket as a result of this, and again, they should contact us directly about this."