Farmers growing cannabis in the UK aren’t dope with suppliers – they’ve been nicking electricity from suppliers to power their plant hothouses.

Up to one third of the electricity stolen each year goes towards powering cannabis farms according to figures from suppliers which is why the regulator Ofgem today put forward new rules for energy firms to weed out the thefts.

The industry detects up to 25,000 cases of stolen electricity each year and estimates this costs consumers at least £200m a year or around £7 per electricity customer.

In 2009 out of 171.9 gigawatt hours (GWh) of power stolen, 55.5GWh was thieved for cannabis farms while in 2010 51GWh out of an estimated total 158.6GWh stolen went to the illegal farms, suppliers believe.

The two most common ways to steal power are by tampering with meters or by passing them altogether, Ofgem told ELN.

To tackle the problem the energy watchdog now wants detecting and preventing theft to be part of suppliers’ licence conditions. They could even face fines if they break these rules.

Suppliers could also have to set up a code of practice on how to investigate thefts and work with agencies such as the Home Office and local police forces to tackle cannabis farms stealing power.

Andrew Wright, Ofgem’s new chief executive said: “Ofgem wants to make sure that consumers are paying no more than they need to for their electricity and lives are not put at risk. It’s critical that suppliers do all they can to clamp down on electricity theft. This is why Ofgem is introducing new rules to encourage better theft detection.

“The reforms build on similar obligations we introduced at the start of this year for suppliers to address gas theft more vigorously,” he added.

The trade body Energy UK said electricity theft is “dangerous and illegal”, adding its members took electricity theft “very seriously”.

The group which represents suppliers said in a statement: “Every year our members detect and prosecute criminals. When energy companies find electricity thieves, they will prosecute. Ofgem’s consultation is a positive move to cut down crime and we look forward to working closely with them, and others in the Industry, on this.”

Ofgem is also pressing suppliers to introduce a 24-hour hotline for customers to report suspected theft. It has set a deadline of 28 August for responses to its proposals.