Tumbling internet access charges in the UK could be abruptly halted if the government forces ISPs to maintain expensive email interception facilities.

Under the Regulation of Investigatory Powers (RIP) Bill, the government wants police agencies to have more control over electronic communications, including the power to intercept email.

Nicholas Lansman, secretary general of the UK Internet Service Providers Association, said service providers are "still in the dark" about how much implementing, maintaining and operating interception facilities would cost.

"Interception involves an added cost when many ISPs are making very small profits or none at all. The government wants lower priced internet access, but it also wants this service done for it," said Lansman, added that it would be difficult to reconcile the two concerns.

The RIP Bill was introduced in the House of Commons on 9 February and is currently going through committee. The Bill regulates investigatory powers in interception of communications, intrusive investigative techniques and access to encrypted data.

Keith Mitchell, chairman of the London Internet Exchange, said the US government set up a budget of $500m (£315m) to implement its Digital Telephony Act, which had similar aims to the RIP Bill. "UK internet providers may have to pay. We're still waiting for a straight answer from the government," he said.

Mitchell also expressed concern that the Bill would set up a more restrictive regime in the UK than in other countries, and will thus drive ecommerce business overseas. Skilled personnel will end up putting in place interception measures rather than building business on the internet, he said.

Richard Clayton of Demon Internet said it would cost ISPs £10,000 a box to set up interception equipment for each modem rack in a service provider's premises. He said the government does not have a proper grasp of the technical issues involved.

"The interception of IP streams is best done in the telco world. In practice it would be much better to put a tap on the telegraph pole," he said.

Home Office Minister Charles Clarke denied that implementation costs would be high, but declined to go into details when questioned by vnunet.com at the Scrambling for Safety conference in London earlier this week.

Brian Gladman, technical advisor to think tank the Foundation for Information Policy Research, said the measures would cost hundreds of millions of pounds, and "apparent government plans to centralise key handling may reduce costs but would be a major security risk".