The Southern Highlands Chamber of Commerce president Berry Mini says the liqour ban put in place in the Papua New Guinea province about two and a half years ago has backfired.
Mr Mini says the ban on selling alcohol was introduced to try and cut down on the number of drunkards in the street and clean up the image of the province to coincide with the arrival of the LNG gas project.
But he says it's not being enforced properly and says some police personnel are assisting contractors to bring liqour into the province.
He says alcohol is being sold on the black market at exorbitant prices and some people are making home-brew or turning to other drugs.
"They can come and buy alcohol but it will be at a black market, it's sold in the town, and marijuana consumption has doubled I think the statistics, I would say. You drive into the town, the main market people are selling marijuana."
Berry Mini says the Chamber of Commerce has urged the provincial government to lift the ban and impose strict controls on the selling of alcohol.