An internet service provider (ISP) has threatened legal action if Lord Mandelson's plan to cut off persistent illegal file sharers' internet connections is approved.

Speaking to The Guardian, TalkTalk, the second largest ISP in the UK with more than four million customers and ownership of the Tiscali and AOL brands, claimed the government's plan was based on file sharers being ‘guilty until proven innocent' and constituted an infringement of human rights.

Andrew Heaney, the executive director of strategy and regulation at TalkTalk, said: “The approach is based on the principle of ‘guilty until proven innocent' and substitutes proper judicial process for a kangaroo court. We know this approach will lead to wrongful accusations.

“If the government moves to stage two we would consider that extra-judicial technical measures and would look to appeal the decision [to the courts] because it infringes human rights. TalkTalk will continue to resist any attempts to make it impose technical measures on its customers unless directed to do so by a court or recognised tribunal.”

James Alexander, media partner at Deloitte, questioned the potential difficulties that ISPs could face in monitoring and blocking users' access. He also claimed that there could be ‘potential damage to an ISP's brand' if they send warning letters to customers who download for legitimate means.

Alexander said: “ISPs will be aware of upsetting legitimate and loyal customers in a fiercely competitive market. ISPs will use the 12-month monitoring period to not only measure the effectiveness of deterrents but also to hone their own detection processes.

“Detection is reliant on a combination of technologies and supporting processes to analyse the huge volume of data generated by all the broadband connections in the UK. Making this detection process efficient and effective may well be a challenge, and while direct costs may be measurable and therefore split with content owners, indirect costs such as managing calls from customers, may be harder to capture.

“This may be easier to swallow if the ISP is also a content owner but may still be a burden for ISPs generally.”