Attacks on Britain’s power network because of cable theft doubled to more than 20 a day in 2011 compared with the year before.

The worrying statistic is driven by high demand for copper with prices of up to $8,000 a tonne this week.

Thieves are targeting the power grid in the hope of selling it on to make a huge profit, according to Tony Glover at the Energy Networks Association.

He told ELN: “They’re targeting a huge range of equipment – overhead power lines, earthing straps in substations, basically they’re going for any piece of copper and brass which they don’t think has electricity running through it. Of course sometimes they make a mistake.”

He said there have been at least six deaths in the last year because of the attack but “almost certainly there have been more”. He added the network staff are concerned “an innocent member of the public” could go the same way as the thieves.

With a brass valve on a transformer costing up to a million pounds, he said, the thefts are proving costly for the industry as well as dangerous.

Tightening up the regulation of the scrap metal trade could make a huge difference.

Mr Glover added: “There needs to be unlimited fines for dealing in stolen metal and the onus needs to be on the scrap metal dealers to ensure they’re not receiving stolen metal. They’ve had it too easy for too long.”