A big rise in the number of cannabis farms has been uncovered since the drug was declassified three years ago, South Yorkshire Police say.
Police have seized £4m of cannabis in South Yorkshire since 2006
Drugs squad officers told the BBC's Inside Out programme they had raided about 50 illegal cannabis factories in Sheffield alone in the last 18 months.
More than £4m of the drug had been seized during that period.
One officer said the "epidemic" of cannabis growing had left police less time to tackle class A drugs.
The Home Office says that cannabis consumption is decreasing, especially among the young.
But South Yorkshire drugs squad officer Det Sgt Bob Chapman told the BBC: "I do think that since it has been declassified, cannabis has certainly become more widespread.
"Our priority as a district drugs team is class A drugs and we are not able to fully focus on class A because of an epidemic of people growing their own cannabis."
Humberside chief constable Tim Hollis, chairman of the drugs committee at the Association of Chief Police Officers (ACPO), said: "I have police officers who go to work on estates where cannabis is rife, they have to deal with young people whose lives have been badly damaged by their addiction to cannabis.
"I find it very hard to go to a public meeting and say cannabis isn't harmful because it is your house being burgled and it is your son or daughter who have started having severe mental and medical problems as a result of their cannabis use.
"Anybody who thinks the solution to the cannabis problem is reclassification is naive."
Inside Out, BBC1 Wednesday 1930 BST