Critics of using foodstuffs to make fuel say the process can drive up food prices by reducing available supplies, hitting the world's poorest people hardest.

Responding to a question in a panel discussion at the Kingsman Dubai sugar conference, Chris Mahoney, director of agricultural products at Glencore, said; "Ethanol production from grains and from edible oil is questionable."

He added, "It has been a factor in creating a higher price environment."

Sunny Verghese, CEO of commodity merchant Olam International Ltd, which trades a range of agricultural commodities, was more critical of the use of corn to make ethanol.

"It is inappropriate. It does not make sense to convert corn to ethanol," Verghese told delegates.

"But it makes sense to convert sugarcane to ethanol."

Later Verghese told Reuters: "I don't believe that converting corn into ethanol helps the food complex. I don't think, given the input-output usage efficiency, it makes a lot of sense to do this."

He did not elaborate.

The Feb. 2-5 Kingsman sugar conference has gathered more than 600 sugar trade leaders from around the world.