Corn-based ethanol is not the main culprit of rising food prices, according to U.S. Department of Agriculture acting Secretary Chuck Conner.

While the rush to make the alternative fuel a staple of U.S. automobile diet has certainly contributed to the increase, most of the blame lies with high oil prices, bad weather, and an ever hungrier China, the official said, according to this Associated Press story.

The White House and agri-business have been pushing vegetable-based fuels as an environmentally friendly and geopolitically secure alternative to pricey, foreign fossil fuels. But corn-based ethanol -- production of which has skyrocketed in recent years -- has raised its own controversy.

Opponents criticize the fuel for being less energy-efficient than other alternatives, such as sugar-cane ethanol and for driving food prices up across the globe. Proponents say that it's greener than most alternatives, and it provides a needed boost to domestic farmers. Ethanol producers' profits, however, are currently being squeezed by a drop in the price of the fuel even as corn prices remain high.