BRUSSELS (Reuters) - The United States and Europe should cut back on production of biofuels because they are hurting food supply at a time of rising prices, an adviser to U.N. Secretary-General Ban Ki-moon said on Monday.

A truck driver unloads his cargo of corn into a chute at the Lincolnway Energy plant in Nevada, December 6, 2007. REUTERS/Jason Reed

Biofuels derived from crops have come under attack in recent weeks on fears they compete with food for farming land and help to push up food prices, worsening a global crisis that is affecting millions of poor.

“We need to cut back significantly on our biofuels programs,” said Jeffrey Sachs, a prominent U.S. academic who is a special adviser to Ban on anti-poverty goals.

“(They) were understandable at a time of much lower food prices and larger food stocks but do not make sense now in a global food scarcity condition,” Sachs told a news conference.

High food and fuel prices have sparked protests and riots in poor countries across the world in the past few months. Many governments have introduced food subsidies or export restrictions to counter rising costs.

“In the United States as much as one third of maize crop this year will go to gas tank. This is a huge blow to the world food supply,” Sachs said before talks in Brussels with EU lawmakers.

EU leaders pledged last year to increase the proportion of biofuels used in petrol- and diesel-consuming land transport to 10 percent by 2020 as part of measures to tackle climate change. Governments are now working on draft EU laws.

Faced with growing unease among EU states over food prices and the biofuels’ green credentials, the European Commission has stuck to the target, but EU Environment Commissioner Stavros Dimas said last month it would be subject to strict conditions to prevent social harm.

The United States is the world’s biggest producer of biofuels. The fuels are made from crops like corn, wheat, sugar and palm oil, which refiners turn into ethanol or oil to replace gasoline and diesel.

Supporters say they are the only renewable alternative to fossil fuels and generally result in lower greenhouse gas emissions.