BTopenworld has become the latest internet service provider to limit the amount of time users can spend online.

Customers on Openworld's Anytime service will find that anytime now means no more than 150 hours each month. Subscribers to its popular Surftime service will be limited to 120 hours a month.

Anyone exceeding these caps will have to have to pay for extra hours online on a pay-as-you-go basis.

BTopenworld said that the new rules offer a "virtually unmetered" service and the vast majority of users there would notice no difference.

Converting to broadband

It wants to encourage heavy users, or abusers as they are often called, to convert to a broadband connection

Dan Stevenson, Jupiter analyst

According to its figures, the average customer spends around 44 hours online each month.

Only 3% of its subscribers are expected to reach the new limits.

In a statement BTopenworld said that the changes, which will take effect from 1 November, were in order to ensure a sustainable business model and to provide the best possible service for its users.

But analyst with Jupiter Research Dan Stevenson said there might be another reason for the decision.

"It wants to encourage heavy users, or abusers as they are often called, to convert to a broadband connection," he said.

He expressed surprise that users who were staying online for such a long time had not already made the shift to high-speed net services.

Bandwidth hogs

Cost might be a barrier as well as the fact that some users would live in areas not served by broadband he said.

The small percentage of heavy users, many of who use up modem space by taking advantage of peer-to-peer file sharing (P2P), have become the bane of the unmetered industry.

Bandwidth hogs slow down network speeds for other users and also disrupt the often tight profit margins in ISPs' business plans.

Unmetered access heralded a new age in internet access, allowing users to stop watching the pay-per-minute clock and have unlimited time online.

Many ISPs found that they needed to cap services as a minority of users spent all day online.

Ideal world

Freeserve now disconnects users who stay online for longer than two hours and are no longer at their PC.

Rival AOL has not yet instigated any caps or disconnects to its unmetered service.

"In an ideal world there wouldn't be a need to limit services," said a spokesman for AOL.

"We can't say never, for example if P2P explodes, but we want to keep it as simple as possible for users and let them get as much access as they want," he said.

"We don't think that placing restrictions on the service is the right way to profitability," he added.