The Dutch city of Utrecht wants to experiment with letting marijuana smokers grow together in co-ops in a bid to improve public health and safety, but the Dutch government is warning against the idea.

The Netherlands tolerates the possession and sale of small quantities of marijuana and allows individual users to grow up to five plants for personal use. But the mass production of marijuana is illegal and puts big bucks in the pockets of organized crime groups.

"We want to tackle this in the experiment. If you have some users grow the cannabis you remove it from the criminal and illegal scene," Utrecht's alderman Victor Everhardt told Dutch public broadcaster NOS on Thursday.

Controlled cultivation would also guarantee quality control and reduce health hazards, Everhardt said.

A Utrecht city council spokeswoman told the Netherlands Information Service the council expects 100 to 150 pot-smokers to be involved and that the experiment should be carried out during the current council's term. She added that plans are in an early stage and more details would be forthcoming.

But the Dutch Ministry of Security and Justice told Reuters the plan was illegal and would be prosecuted if implemented. "The soft drugs policy does not allow for the collection of plants and to grow, for instance, 500 plants," the ministry spokesman said.

That's not surprising from a conservative coalition government that for the past several years has been closing down as many of the country's famous cannabis coffeehouses as it can and is attempting to limit the sale of marijuana to foreigners.