Arrests for possession of cannabis fell by a third in the first year since it was downgraded to a Class C drug, official Home Office figures show.
Arrests for possession take an average eight hours to process
An estimated 199,000 police hours were saved, according to data from 26 of the 42 English and Welsh police forces.
Cannabis was reclassified so that officers could target hard drugs.
Minister Caroline Flint said new crime survey figures also showed that fears for a rise in cannabis use among young people were "wholly unfounded."
Based on the feedback from the 26 police forces, there were an estimated 43,750 arrests in the last 12 months compared with 68,625 in the previous period - a fall of 36%, according to the Home Office.
Ms Flint said: "A year ago we reclassified cannabis on the recommendation of the Advisory Council on the Misuse of Drugs, so that the police could concentrate on the far more destructive Class A drugs.
"One year on, the picture is encouraging, with significant savings in police time which can now be used to drive more serious drugs off our streets and make our communities safer."
She was pleased that critics' predictions for an increase in cannabis use among young people were "wholly unfounded".
"The figures show that young people's cannabis use has remained stable since reclassification and is still significantly down from 1998 levels," she added.
British Crime Survey figures published on Friday show that 24.8% of 16 to 24-year-old respondents reported using cannabis in the last year.
This compared with 25.8% the previous year and 28.2% in 1998.
With each arrest taking an average of eight hours to process, the 24,875 fewer arrests in the year since reclassification meant 199,000 hours of police time had been saved, the Home Office said.
Martin Barnes, chief executive of DrugScope, said the charity would continue to support the reclassification of cannabis.
It was encouraging that cannabis use among young people had been declining but it was "too soon" to draw conclusions from the latest figures.
"Most young people know that cannabis is illegal and can be harmful but we need a much greater focus on drug education and prevention," he said.
"It is concerning that the Government's own schools inspectorate has this week criticised the level and standard of drug education in some schools."