In 2012, a total of 1,047 people were found guilty of cannabis possession, according to figures from the Ministry of Justice.
But by 2017 this number had dropped by 37 per cent to 663.
Of those successfully prosecuted by West Midlands Police, 442 were given a fine or a discharge, while only 14 spent any time behind bars.
West Midlands PCC David Jamieson said the low conviction rate is partly down to a steep reduction in officer numbers.
He said: “There are more than 2,000 fewer officers than there were eight years ago.
“This has led to a combination of two factors, fewer people to enforce the law and with that they have had to focus on issues that cause the most harm, such as violent crime.
“West Midlands Police has not changed its approach, but this is the reality of crime rising and officer numbers falling because of large budget cuts.
“In the West Midlands we are taking a health-based approach to policy reform and we’ve focussed on the harm caused by heroin and crack cocaine as the biggest drivers of violent crime.”
Cannabis possession charges made up 39 per cent of the total drugs possession offences WMP sent to court.
Niamh Eastwood, executive director of drug legislation charity Release, said some police forces had adopted a change in policy and were no longer adopting ‘stop and search’ techniques.
“This trend is welcomed as low-level possession offences should not be a priority for police,” she said.
“That being said over 50 per cent of all stop and searches still focus on this type of activity, with huge disparities in how drugs are policed across the country.
“Some police forces are taking a more pragmatic approach and diverting people away from the criminal justice system for possession offences.”
The Association of Chief Police Officers only recommends arresting someone for having cannabis for personal use after they have first been given a warning and separately, an £80 penalty notice.
A number of PCCs have advocated a shift in drugs policy, including Mr Jamieson, who wants to give away free heroin on the NHS to drug addicts.
Durham Police Chief Constable Mike Barton, who says his force will not prosecute those caught with cannabis for personal use, has called for the drug to be legalised.
“The status quo is not tenable. It’s getting worse,” he said.
“Drugs are getting cheaper, stronger, more readily available and more dangerous. I have come reluctantly over the years to the conclusion that we need to regulate the market.
“If you can regulate the market you can make sure it’s old-fashioned cannabis not skunk or spice.”
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