Stephen Hester, the chief executive of NatWest owner Royal Bank of Scotland, has apologised for technical hitches which left customers unable to pay bills or access their money.

Announcing that the bank would open 1200 branches nationwide today to clear a backlog of chaos caused by a problem with computer software, he said it had let down its customers.

Hundreds of customers have vented their frustration over the problems, with some finding payments had gone awry and others observing disappearing wages, or holidays and home purchases disrupted.

Account balances were not updated properly overnight, meaning credit and debit payments were not showing up as quickly as they should.

In a statement, Hester 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 - 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 around the clock to resolve these problems as quickly as we are able."