Barclaycard customers have been unable to access their online accounts for more than a week because of "high demand" for the service. The website first crashed on Monday last week and access has not been fully restored since.

A spokesman for the company said: “We fully understand how frustrating this must be for our customers and our doing all we can to solve the issue. In the meantime, we apologise unreservedly.”

He added: ”We increased capacity by 50 per cent last week and we're currently testing further fixes to solve the problem - we can't give a date for further capacity but hopefully in the near future. I can also confirm that things have improved over the last two days”

But the company’s customers have been left fuming. One irate cardholder who contacted Times Online said: “Telephone support is non existent, e-mails aren't answered. All they say is "high demand". There is something strange going on but they won't tell us and won't fix it. Is there a major security breech, is it just incompetence or what?”

The website outage caps a bad couple of weeks for Barclaycard, which has 10 million customers in the UK. On Friday last week Ofcom fined the company £50,000 for making “an extremely high number” of silent calls to its customers. The communications regulator said it was the worst case of silent calling it had ever seen.

Silent calls are generated when call centres using automated calling systems generate more calls than their agents can deal with. When the person called answers the telephone, there is no agent available, resulting in silence on the line.

Customers who need to find out any details about their account can contact Barclaycard’s customer services on 0844 811 9111.