UPDATE 1-Biofuels blamed for food price crisis-report

(Adds details and Zoellick comments in paragraphs 5 to 8)

LONDON, July 4 (Reuters) - Biofuels have forced global food prices up by 75 percent -- far more than previously estimated -- according to a confidential World Bank report published in a British newspaper on Friday.

The assessment is based on a detailed analysis by Don Mitchell, an internationally respected economist at the Washington-based global financial body, the Guardian said.

The figure contradicts U.S. government estimates that plant-derived fuels have contributed less than 3 percent to food-price increases, the newspaper said.

It will add to pressure on governments in Washington and Europe, which have turned to biofuels to reduce emissions of greenhouse gases and reduce their dependence on imported oil.

Due to Friday's Independence Day holiday in the United States the Guardian report could not immediately be confirmed.

World Bank President Robert Zoellick has said biofuels are a "significant contributor" to the increase in food prices.

Recently, he wrote in the Financial Times that the use of corn for ethanol by the United States had consumed more than 75 percent of global corn production over the past three years, and called on the United States and Europe to ease subsidies and tariffs on biofuels derived from corn and oilseeds.

"The use of corn for ethanol has consumed more than 75 percent of the increase in global corn production over the past three years," he wrote. "Policymakers should consider 'safety valves' that ease these policies when prices are high," he wrote.