A spiralling drug trafficking problem in Venezuela has been made worse by official corruption and a refusal to co-operate with the US, according to a forthcoming US Congress report.

A copy of the report, obtained by the Financial Times, showed that efforts to combat a fourfold increase in cocaine smuggling through Venezuela between 2004 and 2007 have been damaged by corruption in the national guard, which, it says, co-operates with Colombian drug traffickers.