Speaking at the UN in New York, Bolivian President Evo Morales said the development of biofuels harmed the world's most impoverished people.
And President Alan Garcia of Peru said using land for biofuels was putting food out of reach for the poor.
Meanwhile UK Prime Minister Gordon Brown is hosting a meeting to discuss European policy encouraging biofuels.
Ahead of the meeting, Mr Brown said that the UK should be "more selective in our support"for biofuels, which convert cereals into fuel.
Campaigners say providing a renewable alternative for conventional fuels could help stop global warming.
But as food prices climb worldwide, there is a fear that development of biofuels could reduce the production of badly-needed basic foodstuffs.
