Greater Manchester's police force area had the second highest number of cannabis factories found in the UK last year.

The force found 32 factories per 100,000 in 2009/10, the second highest ratio of any force, the figures from the Association of Chief Police Officers (Acpo) showed.

The North Yorkshire force recorded the highest rise in the number of factories found, up 1,200% to 13 last year from just one in 2007/08 - but the force does not experience a large number of factories compared with other areas, the report found.

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.

Acpo also found that the premises used for cannabis cultivation were becoming more varied and included industrial buildings, former pubs, cinemas, nightclubs, hotels, print works and even banks.

The report, called the UK National Problem Profile: Commercial Cultivation of Cannabis, also found that criminals involved in the cannabis farms were also involved in crimes such as counterfeiting currency and DVDs, money laundering, immigration crime, firearms, blackmail, prostitution, theft and people trafficking.

Reports of factories being taxed by other criminals has also led to criminals arming themselves with machetes, sawn-off shotguns and stun guns, Acpo said.

More discreet weapons, including a mobile phone and a torch with electrodes on the top which caused shock when in contact with skin, were also found.

Some forces also reported that a small number of factories featured booby traps, including attempts to electrify window frames and door knobs, a home-made device which would detonate a shot gun cartridge and a window criss-crossed with bare wire attached to a standard three-pin plug," the report said.

In another instance, an external side gate at a factory was wired directly to the mains.