Bioenergy produced from crops does not threaten food supplies, researchers funded by the U.S. government, World Bank and others said in a report on Tuesday, dealing a potential blow to critics of the country's biofuels program.

There is no clear relationship between biofuels and higher prices that threaten access to food, as some prior analysis has suggested, according to the research partly funded by the U.S. Department of Energy.

Environmentalists and others have long argued that the increased use of ethanol, produced from corn in the United States and sugarcane in Brazil, threatens global food security, which the World Health Organization defines as "access to sufficient, safe, nutritious food." Critics of biofuels, which are used for transportation, say they could threaten food supplies.

"There may not be as tight a link as people think" between commodities prices and food security, Siwa Msangi, a co-author of the paper and senior research fellow at the International Food Policy Research Institute, said in an interview on Tuesday.

A 2012 drought in the United States that slashed corn output, for example, caused ethanol plants to shutter or reduce output but not a notable change in food prices, the report said.

Policymakers including U.S. Senators Pat Toomey and Dianne Feinstein have criticized a more than decade-old biofuels program that requires increasing amounts of renewable fuels be blended with gasoline and diesel.

The U.S. Renewable Fuel Standard (RFS) was created in 2005 in a bid to reduce dependence on foreign oil and cut greenhouse gas emissions, but has been mired in a years-long debate between biofuels advocates, environmentalists and oil companies.

Research shows the standard has caused grasslands and wetlands to be converted into farms to produce biofuels, said Emily Cassidy, a research analyst with the Environmental Work Group, which has criticized the RFS.

"Most biofuels are made from food, like corn and soy, which competes for feed and animal feed production. That ultimately has a big impact on markets," Cassidy said.