More than 6,800 cannabis farms and factories were discovered by police in the UK last year, figures have shown.
A report by the Association of Chief Police Officers (Acpo) said almost 20 commercial cannabis factories were being found by police every day, taking the total for 2009/10 to 6,886 - more than double the 3,032 discovered two years ago, and more than eight times the annual average between 2004 and 2007.
Commander Allan Gibson, the Acpo lead on cannabis, said the findings came as no surprise and the rise was in part down to an increased focus on the issue by the authorities.
"The police response is now stronger and more effective through better coordination and intelligence sharing between forces and other agencies and more covert operations against the operators," he said.
"The level of publicity around cannabis since its reclassification in 2008 has meant that more members of the community are now reporting any unusual signs of habitation in buildings and houses, which is leading to more detections.
"This profile gives us a better understanding of the current picture of the commercial cultivation of cannabis in the UK and the need for continued robust enforcement."