Cable giant NTL has been forced to suspend all advertising for its free ISP service NTL World after being overwhelmed by demand.
The company has received 600,000 registrations for the service, which it first advertised just over a month ago. The service promises free unlimited access to the Internet for its telephone subscribers.
Only a fraction of the registrations have made it online, although the company is refusing to reveal the exact percentage.
It is phasing new users onto the system when it can cope. Once the backlog of applications has been cleared it will let more people register to use the service.
The campaign, by J Walter Thompson, includes TV, poster and press ads and is believed to have cost more than £4m.
The Advertising Standards Authority is threatening to launch an investigation after receiving complaints from angry customers.
An NTL spokesman says the company did not anticipate how long people would spend online, leading to potential snarl-ups. “People are taking advantage of the free access by spending much longer online. Our focus is now on clearing the backlog so there is little point in advertising.”