REPORTS of suspected cannabis factories have increased by more than 20 per cent in Yorkshire since residents were given new "scratch and sniff" cards.

Crimestoppers worked with 17 police forces earlier this year to help residents identify the smell of cannabis, so they could report when they smelt it.

About 10,000 cards were handed out in York, Selby, Harrogate, Scarborough, Northallerton and Skipton in June.

A spokeswoman for Crimestoppers could not narrow down their results to the York area, but said there were 117 reports in the month following the campaign, a 21 per cent increase on the month before.

Detective Inspector Jason Marchant of North Yorkshire Police’s Organised Crime Unit, said: "This is good news for the police as this type of information is vital in the fight against crime in our communities.

"Cannabis cultivation fuels wider criminality including modern slavery. Sometimes people working in the ‘farms’ have been victims of human trafficking who are working there against their will or vulnerable members of the public intimidated into working for a criminal gang.

"We urge members of the public to keep on reporting their suspicions to us as every little piece of information we are given, goes to form part of a bigger picture which helps the police to disrupt criminal activity and bring the perpetrators to justice."

Following the campaign, a number of high value cannabis farms around the country have been shut down by police, including a haul of 500 plants in Hampshire, with an estimated street value of more than £700,000.

To report information to the police, phone 101, or pass information anonymously to Crimestoppers on 0800 555 111.