Sean Sloan says this week's Barclays blunder has left him feeling a lot less confident about online banking. Mr Sloan, 32, was one of those who logged on to the bank's net service on Monday morning and suddenly found himself staring at another customer's account details, writes Rupert Jones .

"This someone had a business account and a personal account. I could see all the balances, account numbers and sort codes." He was able to see that the person had made a payment the day before for £13,000. The screen also offered a number of options such as transferring funds or making payments.

"I realised Barclays must have made a mistake. The first thing I wanted to do was get out of there - if funds did go missing from this account, I didn't want to be blamed for it. So I got out," says Mr Sloan, of Tottenham, north London, a director of a company called Snowchicken who works from home.

He ran downstairs and phoned Barclays' helpdesk - it was 8.30am. "I told them I was really concerned - if I can see someone else's details, what's stopping someone seeing my details and transferring funds?" He was told someone would phone him back. But despite ringing again, by mid-afternoon he had still heard nothing. When he mentioned the BBC had been round to film him for that night's news, the bank's head of online banking called back and couldn't apologise enough.

He says Barclays should have shut the service down sooner. He adds: "I enjoy online banking - it saves me standing in queues. But this has put doubts in my mind. If it can happen once, what's to stop it happening again?"

The bank says: "Our service is safe. We have not had these problems before. We invest a lot in our security systems and are committed to ensuring this does not happen again."