Bolivia is set to withdraw from an international narcotics convention in protest at its classification of coca leaves as an illegal drug.

President Evo Morales, who is also the leader of one of the country’s main coca producers’ unions, has asked Congress to pass a law that would take Bolivia out of the 1961 United Nations Single Convention on Narcotic Drugs.

The government says that the convention contravenes the Bolivian constitution, which states that the country is obliged to preserve and protect the chewing of coca leaves as a cultural heritage and ancestral practice.

Bolivia has long argued that coca in its natural state is not an illicit drug. The plant is legally grown in the country for medicinal and traditional purposes. An international attempt to remove its chewing from the UN list failed in January, so the government now wants to withdraw from the convention altogether.

Under the draft law, which has already passed the lower chamber of Congress and is likely to pass in the Senate, where Morales’s party has a two-thirds majority, Bolivia would keep its international obligations in the fight against drug trafficking. Foreign minister David Choquehuanca said the country could rejoin the convention next year, but with a reservation: that it be allowed to consume coca legally.

"[This] is an attempt to keep the cultural and inoffensive practice of coca chewing and to respect human rights, but not just of indigenous people, because this is an ancient practice of all Bolivian people," Choquehuanca said.

Opposition politicians argue that the government is surrendering to traffickers. "Internationally, we’re giving a bad impression as a country," said opposition congressman Mauricio Muñoz. "There will be disastrous and irreversible consequences for Bolivia. And we think this is the wrong path the president is taking, not to fight drug trafficking head on."

Bolivia is the third largest coca producer in the world, much of which is diverted for making cocaine for Brazilian and European markets. But while recently admitting that coca cultivation has grown in the country, Bolivia maintains that it cannot defeat drug traffickers without a reduction in the consumption of cocaine in the west.

Arce aseguró que esa ley "no debe inquietar a nadie" porque la denuncia señala que el país se retira de ese tratado, pero eso no impide que el país, por propia determinación, siga cumpliendo las determinaciones de lucha contra el narcotráfico.