Biofuels have caused world food prices to rise by 75% - far more than previously estimated - according to a secret World Bank report.

The report contradicts US claims that biofuels contribute less than 3% to food price rises, according to the Guardian, which obtained the document.

“Without the increase in biofuels, global wheat and maize stocks would not have declined appreciably and price increases due to other factors would have been moderate,” the report stated.

Although the report was completed in April, it had not been published to avoid embarrassing the US government, senior development sources told the Guardian.

A UK report into the impact of biofuels is due to be released next week and is expected to reveal that biofuels have made a “significant” contribution to soaring food prices.