People who grow their own cannabis should face lighter penalties to end their contact with criminal suppliers, an influential think tank tells the Home Office.
Relaxed laws have provoked controversy
Half the cannabis consumed in England and Wales is now home-grown, research from South Bank University and the National Addiction Centre found.
The study also found the market in domestic cultivation is supported by a thriving, legal trade in cannabis seeds and horticultural equipment.
Experiments in tolerance of possession of the drug in Lambeth in London and moves to downgrade cannabis's classification to class C have previously attracted criticism.
The Joseph Rowntree Foundation is behind the pressure to change the law for home-growers, pointing out that 243 people were jailed in 2000 for growing cannabis.
They say there are wide variations in the way different police forces treat the crime.
could be forced to abandon the cannabis market altogether
Professor Mike Hough
Some charged growers with production - which has a mandatory seven-year
sentence for a third conviction - while other forces opted for the more minor offence of cultivation.
The reclassification of cannabis is likely to be finalised over summer, with the downgrading meaning possession will only be an arrestable offence in extreme circumstances.
Professor Mike Hough, co-author of the report entitled A Growing Market, said: "If small-scale home cultivation attracted an on-the-spot warning rather than a caution or a court conviction, it is likely that more users would switch to growing their own and stop buying from dealers.
"Large minorities of young people use cannabis.
"It is essential to insulate them as much as possible from drug markets
operated by dealers who sell not only cannabis but crack and heroin.
"As their profits from cannabis sales diminished, criminal entrepreneurs
could be forced to abandon the cannabis market altogether."
New offences of "social supply" and
"social cultivation" if the drug is grown for the use of friends could be one option, although the Home Office has previously dismissed this.