A US proposal to begin widespread aerial spraying of opium poppies in Afghanistan came under fire at a donor conference in Tokyo yesterday, highlighting a split between the US and its allies over drugs and security policy in the country.

William Byrd, a World Bank economist and adviser on Afghanistan, told a press conference: "International experience suggests [spraying is] not sustainable, either politically or economically." The bank and the UK government are instead seeking support for a broad package of economic measures to wean Afghanistan off the opium trade, the country's biggest industry and source of more than 90 per cent of the world's heroin, says the United Nations.