Biofuels have forced global food prices up by 75% – far more than previously estimated – according to a confidential World Bank report obtained by the Guardian. The damning unpublished assessment is based on the most detailed analysis of the crisis so far, carried out by an internationally-respected economist at global financial body.

The figure emphatically contradicts the US government’s claims that plant-derived fuels contribute less than 3% to food-price rises.