How much do biofuels drive up food prices?

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The damning unpublished assessment is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. It
will add to pressure on governments in Washington and across Europe,
which have turned to plant-derived fuels to reduce emissions of
greenhouse gases and reduce their dependence on imported oil.

Here is the story, the report is not yet available, at least not to me.  Seventy-five percent seems like a high estimate to me, especially since many foods are more expensive but they are not all used for biofuels.  Still, the government’s estimate of three percent is surely way too low.  Biofuels are maybe a good test case for various estimates of government quality: will the bad biofuels still be subsidized five years from now?