Cannabis factory fires have more than doubled in the last two years, according to new figures.

Figures released this week by the London Fire Brigade show that in 2012/13, there were 27 cannabis factory fires in London, compared with just 13 in 2010/11.

In 2012 there was one fire a fortnight in buildings being used to cultivate the Class B drug. The figures also show that 25 of the 27 fires last year were in residential properties posing a significant risk to homes next door.

On average, it requires four fire engines and more than 20 firefighters to bring cannabis factory balzes under control, and can be extremely dangerous due to the large amount of heating and lighting equipment used to grow the plants.

The Brigade is extremely concerned about the increase of these fires, and the greater risk firefighters put themselves through to tackle such blazes.

London Fire Brigade Third Officer Dave Brown, said: "Cannabis factory fires can be severe due the way criminals use unsafe wiring to illegally obtain electricity in order to grow the plants.

"They’re often in top floors or lofts which means when a fire takes hold it spreads, destroying roofs and damaging neighbouring buildings.

"Firefighters can also be exposed to risks when dealing with the fires due to dodgy wiring and booby traps at some of the properties.

"It’s important that people know the key signs and inform the police so that they can act swiftly to prevent these dangerous fires."

In 2011/12, there were 19 Cannabis factory fires in London.