Private cannabis farming in Britain has a growth spurt

10 millions adults aged 16-59 who have used cannabis, making it the most widely consumed narcotic (AP)

Against the steady hum of an extractor fan, the handheld video camera pans over a small forest of green plants. The unmistakable serrated leaves of cannabis flutter as gentle gusts of warm air from a nearby heating unit waft over them.

The man who uploaded the video onto YouTube can barely contain his excitement. "There's a lot of branches," he squeaks. "These plants are getting nice and bushy really fast thanks to the hydroponics. It took me about an hour to make this hydroponics kit so if you want me to make you one, let me know and I can ship it to you."

Given the current economic conditions, the Government is keen to encourage all sort of new entrepreneurial initiatives. But the rapid growth of Britain's private cannabis farms is probably not quite what the Treasury had in mind.

A clandestine industry has sprung up in the bedrooms, living rooms, cellars and rooftops of Britain's pot heads. Some do it for personal consumption, others do it to make extra cash at weekends. Others grow cannabis for organised criminal networks that make millions out of what they know is a comparatively low- risk, high-profit crime.

The expansion of Britain's pot farms has been so rapid that police say they are now raiding as many as 20 illegal plantations a day. More than 7,000 farms were detected last year compared to 3,000 three years earlier. Figures released yesterday by Newcastle University suggest as much as £200m worth of electricity is stolen every year by growers – many of whom are siphoning power directly from the mains supply to avoid suspiciously high electricity bills. In the past week alone raids have been reported in Nottingham, Sunderland, and Kensington in London.

A national project has also found that of 7,000 identified groups of organised criminals, a fifth are involved in cannabis cultivation or trafficking. Robberies, burglaries and violence with guns have all increased because of the competition between rival groups.

For people like Jim, a 22-year-old mechanic from Yorkshire, the lure of easy money is simply too good an opportunity to pass up. He has been growing cannabis for the past five years, mainly at a friend's house. After learning how to grow plants properly he soon realised he had green fingers which could turn the sticky, sweet smelling buds into hard cash. "I usually just get rid of big amounts like pounds at once because it is too risky going little," he told i. "I make around £10,000 every four months."

British gangs have increasingly moved into the business, which used to be dominated by South-east Asian gangs. Without the problem of having to elude border controls and without high costs of transport, the crops have become attractive to domestic criminals.

The "gardeners" typically include criminals forced to work in factories to pay off "debts" to gangs, perhaps because of lost consignments of drugs. Others look to hide the factories in industrial areas so the heavy use of electricity is less likely to be spotted. Daniel Lloyd, a businessman who runs an industrial park in Telford, Shropshire, said police recently raided a unit and discovered a secret farm.

"We had no idea it was there," he said. "The man told us he needed a place to store gardening equipment and we leased him a unit. When the police raided it we discovered that he had laid out an entire farm with foil sheeting, heat lamps and insulation. Apparently he was shopped by a disgruntled friend."