Arrests for cannabis possession in England and Wales have dropped by 46% since 2010, figures obtained by BBC Breakfast suggest.
Cautions fell by 48% and the number of people charged fell by 33%, according to data from police forces released under the Freedom of Information Act.
Crime survey data suggests cannabis use remained roughly level from 2010-15.
One force which no longer targets cannabis users said officers had been "freed up" for "more important" work.
The Home Office said all crimes reported to the police should be taken seriously, investigated and, where appropriate, taken through the courts.
"Decisions on individual investigations are an operational matter for Chief Constables based on the evidence available to them," a spokesperson said.
Of the 43 police forces contacted by BBC Breakfast, 32 responded with full data.
The figures showed that, from 2010-15, the number of:
- arrests for cannabis possession fell from 35,367 to 19,115
- cautions for possession fell from 9,633 to 5,036
- people charged for possession dropped from 15,366 to 10,220
Arrests for possession with intent to supply remained about the same - 4,934 in 2010 and 5,012 in 2015.
Last July Durham Police said it would no longer target or investigate cannabis users or those growing the class-B drug for their own use.
Asked if this was sending out a message that smoking cannabis was acceptable despite being illegal, Chief Constable Mike Barton said: "I'm not condoning drug use. I never have.
"It's freed up our staff to deal with things that are more important."
He told the BBC his force still had "zero tolerance" for drug dealers.
The Crime Survey for England and Wales asks people aged 16-59 if they have used cannabis in the last year, and the figure of about 7% who say they have has remained steady from 2010-15.
One cannabis user, Jonathan, told the BBC he used cannabis for medical reasons but supported legalisation for both medical and recreational purposes.
He dismissed suggestions that this would lead to more young people using the drug, saying it was currently easier for them to get cannabis than alcohol because the sale of alcohol is regulated.
But Craig, a former cannabis user, said it "robbed" him of 10 years of his life and led to experimentation with other drugs, including heroin.
He said it was "crazy" to legalise cannabis.