AMSTERDAM, Netherlands — A broad coalition of political parties unveiled a pilot program Friday to regulate marijuana farming on the model of tobacco. Opponents say the plan would be tantamount to legalizing growing the drug.

Under the test program, to be conducted in the southern city of Maastricht, existing health and safety standards will apply to growers, and they would no longer be the target of police raids or prosecution.

Coffee shops permitted to sell marijuana would be required to provide consumers with information about the health hazards of smoking — similar to tobacco companies — and the chemical content of the marijuana. The shops would also have to say where they bought the marijuana they sell, which proponents say will deter growers from operating dangerous underground greenhouses.

Under current Dutch policy, marijuana and hashish are illegal, but police don’t prosecute for possession of less than one ounce. Authorities also look the other way regarding the open sale of cannabis in designated coffee shops.

But commercial growing is outlawed, giving rise to a contradictory system in which shop owners have no legal way to purchase their best-selling product.

Dutch mayors along the country’s borders have lobbied hardest for the change, which they say would make it more difficult for German and Belgian drug tourists to smuggle large quantities of marijuana out of the country.

“It will be possible to trace where cannabis is grown and where it’s sold,” said conservative lawmaker Frans Weekers.

Opponents, however, have argued that regulation could open the door to outright legalization of marijuana in a country that already has some of Europe’s most lenient drug laws. Prime Minister Jan-Peter Balkenende and his ruling Christian Democrat Party said regulating marijuana cultivation would set the Netherlands another step apart from the rest of the continent.

“This experiment would be at odds with Dutch law, and there’s a legal problem” internationally, as well, Balkenende said.

The Justice Ministry has ordered an investigation into whether the plan would violate international law. The findings are expected within several days.

Weekers said the current policy is “leading to increasing problems.”