British Telecom's image has taken another blow after it was forced to withdraw an advert claiming its internet service was "fast and reliable".

BT has been forced to pull the ad because its service is not "fast and reliable" as it claimed, the advertising standards authority has ruled.

BT removed the advert after the advertising watchdog received complaints from members of the public who found the BTinternet Anytime service unreliable at busy times of the day.

Problems were found with BT's telephone exchanges, which were unable to connect users even though "gateways" for internet access were available, causing customers to receive a busy signal.

Several people wrote to the ASA after experiencing problems and complained about a banner advertisement on a website stating, "BT Anytime for a fast, reliable service".

The ASA said the advert was misleading and BT removed it from the website until the problems could be solved.

The ASA ruled: "Because intermittent and ongoing problems were preventing some customers from connecting to the internet, the authority considered that the advertisers' claim that their service was reliable was misleading."

BT has promised to fix the problem and said it would monitor the exchanges and provide customers having difficulties with an alternative, free dial-up number.

The company recently announced plans to rebrand all its internet offerings under the name BT Openworld, backed by a multimillion pound marketing campaign.