The United Nations has renewed its warnings to Uruguay and the US states of Colorado and Washington that their cannabis legalisation policies fail to comply with international drug treaties.

The annual report from the UN’s International Narcotics Control Board, which is responsible for policing the drug treaties, said it would send a high-level mission to Uruguay, which became the first country to legalise the production, distribution, sale and consumption of cannabis for recreational purposes.

The UN drug experts said they would also continue their dialogue with the US government over the commercial sale and distribution of cannabis in Colorado and Washington state.

The possession and cultivation of cannabis became legal on 26 February inWashington DC. Voters in Oregon and Alaska have also approved initiatives to legalise the commercial trade in cannabis for non-medicinal purposes.

The INCB said it “continues to engage in a constructive dialogue” with the US government on cannabis developments and it is clear the...