Colombia's largest left-wing rebel group, the Farc, has presented its proposals to regulate drug production.
The Farc presented the plan as part of its peace talks with the government.
The guerrilla group, which largely finances itself through drug trafficking, suggested a programme to "regulate the production of coca, poppies and marijuana".
The rebels said that growers should be enticed "to voluntarily grow alternative crops".
Along with Peru and Bolivia, Colombia is one of the world's top three producers of coca, the raw material for making cocaine.
It also grows large amounts of marijuana and produces smaller quantities of heroin.
The government has spent millions of dollars trying to eradicate illicit crops - pulling them out by hand, spraying them with herbicides, and encouraging growers to switch to legal alternatives.
According to United Nations figures, Colombia has seen a 25% fall in the area of land planted with coca between 2011 and 2012.
But Farc negotiator Pablo Catatumbo said prohibition and eradication were not the way forward.
"Instead of fighting the production [of illicit substances] it's about regulating it and finding alternatives," he said.
"The fundamental basis of this plan lies in its voluntary and collaborative nature, and in the political will on the part of the growers to take alternative paths to achieve humane living and working conditions."
Mr Catatumbo also said that the "medicinal, therapeutical and cultural" uses of the substances should be taken into account.
In Bolivia, the production of coca in small amounts is legal although the production of cocaine remains banned.
Coca leaves have been used for many centuries as a mild stimulant and to counteract the effects of high altitude in the Andes.
Last month another South American nation, Uruguay, voted to legalise the marijuana trade, becoming the first country in the world to do so.
The Farc has been engaged in peace talks with the Colombian government for more than a year.
The two sides have reached tentative agreements on two issues so far - land reform and the eventual political participation of the rebels should a peace treaty be signed.
They are currently holding their 19th round of talks in the Cuban capital, Havana.