TOKYO, Japan — Prime Minister Stephen Harper conceded Thursday that biofuels are "probably'' a small factor in the rising cost of food.

But he says the rise in energy input costs is likely a far bigger factor in the rise of food prices around the world.

The Conservatives pledged in the last federal election to make all fuel contain five per cent biofuel, such as ethanol and biodiesel, by 2010.

A newly-passed law does just that.

At $2.2-billion, federal support for Canadian biofuels is the government's most expensive environmental program.

Harper last week appointed Kory Teneycke, the former executive director of the Canadian Renewable Fuels Association, as his new communications director.

Some biofuels are derived from corn, wheat and straw.