New Liberal Democrat leader Sir Vince Cable has said the party will continue to support the legalisation of cannabis.
Sir Vince said it was better to control the drugs industry rather than having "free market anarchy".
It continues a long-term commitment to legalisation by the Lib Dems.
The Home Office said it has no plans to legalise cannabis, as there is "clear scientific and medical evidence that cannabis is a harmful drug which can damage people's mental and physical health".
However, Sir Vince told BBC Newsbeat there were "serious negative side effects from driving it underground".
He added: "The evidence is clear that if you want to stop abuse and damage to young people, you've got to bring the trade into the open and out of the hands of the criminal underworld.
"Common sense suggests to me that you should try to regulate and control this market, rather than just have a free market anarchy in the underground, which is what happens at the moment."
The Home Office said its independent experts, the Advisory Council on the Misuse of Drugs, said using cannabis is a significant public health issue and can "unquestionably" cause harm.
It added that legalisation would not eliminate the crime committed by the illicit trade, and would send the wrong message to the vast majority of young people who do not take drugs.