UK government proposals to make ISPs take action against the estimated six million users who access pirated online material every year could prompt an explosion in Wi-Fi hijacking, experts warned today.

Security firm Sophos predicted that the moves outlined in a Green Paper could cause headaches for ISPs and Wi-Fi users, as users could claim that other people have been illegally piggybacking on their internet services.

A Sophos poll of 560 computer users in November revealed that 54 per cent have stolen Wi-Fi internet access in the past.

"Pressure is being put on ISPs to take action, but an open Wi-Fi hotspot may mean that it is you who ends up disconnected from the net while your next door neighbour is happily watching the Hollywood blockbuster they stole via your connection," said Graham Cluley, senior technology consultant at Sophos.

"People who illegally download material from the net are not going to have any qualms about stealing someone else's internet connection.

"The widespread scale of the problem not only means that there are likely to be innocent victims, but it gives those people who have been making illegal downloads a plausible defence."

The Green Paper, which is due to be published next week, outlines a 'three-strikes' initiative under which users making illegal downloads will first receive an email warning, then a suspension of their account, and finally termination of their contract.

"ISPs are finding themselves between a rock and a hard place. They are being leaned on by the movie and music industry to block pirate downloads, but don't want to alienate customers by accusing them of something they didn't do," Cluley added.

"There is no 100 per cent solution for blocking illegal downloads which does not also inconvenience the innocent."