After years of sniffer dogs, UK authorities are looking to train people to smell out pot growers in their own communities.

Crimestoppers UK, along with local police forces, are distributing 200,000 'scratch and sniff' cards that smell like cannabis plants.

The charity says that while many people know the smell of cannabis when it is burning, they are not familiar with its scent when the plant is growing.

Crimestoppers says there has been a 15 per cent increase in illegal cannabis farms in the UK in the last two years.