Many customers across its former Telewest franchise area tried to logged onto the internet on both Monday and Tuesday and found their broadband connection unavailable or performing poorly.

The problem was caused by a loss of synchronisation of dynamic customer IP addresses. Anyone who turned off the power to their modem during the outage period could have been affected, the company says.

The problem arose around 4pm on Monday afternoon. The spokeswoman claimed that affected users were reconnected by 9pm on Monday. However, one NTL:Telewest user told ZDNet UK of continuing problems around 9am on Tuesday morning.