The website of online bank Egg has suffered a serious outage that the bank is blaming on a problem at Cable & Wireless, its telecoms provider.

The service went down at 7pm on Wednesday and at 3pm Thursday only some service had been restored. A spokesperson said at 3pm that about a quarter of customers could access the site, but it was hoped that full access could be restored within the hour with the help of Cable & Wireless.

Egg said it was reliant on Cable & Wireless to sort out the problem and couldn't fix it alone, though it was doing all it could.

A spokeswoman said the web downtime was a "massive priority" for the bank, but said the call centre had operated normally throughout the web service interruption.

She said up to 50 other firms had been affected by the Cable & Wireless problems, and the telecoms provider admitted several customers had been hit.

"Since yesterday afternoon, we've been experiencing some issues on our network meaning that a handful of our customers are experiencing intermittent, slow or no access to their Internet and email services", C&W said.

"While we isolate and fix the root cause of the issue, we're putting in re-routes for our customers to take them away from the fault and restore their services."