The United Nations Special Rapporteur on the Right to Food is demanding an international five-year ban on producing biofuels to combat soaring food prices.
Switzerland's Jean Ziegler said the conversion of arable land for plants used for green fuel had led to an explosion of agricultural prices which was punishing poor countries forced to import their food at a greater cost.
"232kg of corn is needed to make 50 litres of bioethanol," Ziegler said on Thursday. "A child could live on that amount of corn for a year."
Using land for biofuels would result in "massacres", he said, predicting a reduction in the amount of food aid sent to developing countries by richer ones.
"It's a total disaster for those who are starving."
Ziegler's proposal for a five-year moratorium, which he plans to submit to the UN General Assembly on October 25, is aiming to ban the conversion of land for the production of biofuels.
Ziegler said he hoped that by the time the moratorium was lifted science would have made sufficient progress to be able to create "second generation" biofuels, made from agricultural waste or from non-agricultural plants such as jatropha, which grows naturally on arid ground.
Taking Brazil as an example, Ziegler said he deplored the fact that sugar cane plantations, whose products were used for biofuels, were spreading at the expense of food-producing land.
He said ten hectares (100,000 square metres) of food-producing land could sustain an average of seven to ten farmers, whereas the same area could only produce enough sugar cane for one farmer.
Threat to poor
Only two years ago, with the twin spectres of peak oil prices and climate change looming, biofuels seemed the ideal alternative energy.
Now it is the poor who have to contend with the flip side of biofuels: spiralling cereal prices, say experts.
"The days of cheap food are over," said Joachim von Braun, director of the International Food Policy Research Institute, in an article for the Swiss Agency for Development and Cooperation (SDC) in September.
Over the past decade, while production of biofuels using corn, sugarcane, soybean and other staples has risen dramatically, malnutrition has continued. Nearly 900 million people worldwide suffer hunger, 70 per cent of them food producers, peasants and rural dwellers.
Von Braun warns this figure could hit one billion in just a few years and that rising demand and increased bioenergy costs are affecting food prices.
"The bioenergy market receives considerable state funding and is dominated by the heavyweights in the oil, cereal and automobile industry," he said.
"Barring technological progress and enactment of regulations based on transparent standards, we are looking at a 20-40 per cent increase in food prices between now and 2020. And the poorest, some of whom live on 50 cents a day, will be unable to foot the bill."
A study commissioned by the Swiss authorities in May also concluded that biofuels might not be the panacea for the world's fossil-fuel woes.
Such fuels, touted as an ecologically friendly source of energy, might be more harmful for the environment than their fossil counterparts, it said.
According to the authors, while it was true that biofuels might emit less greenhouse gases than fossil fuels when consumed, producing them was generally more stressful on the environment.
Growing and processing crops for energy purposes or feedstock can have the heaviest environmental impact, as soil quality can be affected adversely, for example through fertiliser overuse.
swissinfo with agencies
Biofuels contributed 0.3% of total energy consumption in European Union countries in 2003, which rose to 2% last year.
The EU wants to raise that level to 5.75% by the end of 2010. France has the more ambitious goal of consuming 7% biofuels in 2010 and 10% in 2015. Bioethanol fuel in Spain already accounts for 3% of the total consumption.
The US has announced it wants bioethanol to make up 10% of all car fuel consumption by 2010.
Biofuels are any kind of fuel made from living things, or from the waste they produce.
Biofuels should produce less greenhouse gas emissions than conventional transport fuels.
Burning the fuels releases carbon dioxide but growing the plants absorbs a comparable amount of the gas from the atmosphere.
However, energy is used in farming and processing the crops, and this can make biofuels as polluting as petroleum-based fuels, depending on what is grown and how it is treated.
Production of ethanol doubled globally between 2000 and 2005, with biodiesel output quadrupling. Brazil leads the world in production and use, making about 16 billion litres per year of ethanol from its sugarcane industry.
The United States holds the same position for corn and together they make up 70% of the global market. 60% of new cars can run on a fuel mix which includes 85% ethanol.
Jean Ziegler is a former professor of social science and economics at the universities of Geneva and the Sorbonne in Paris.
The 73-year-old Ziegler has a reputation as an outspoken critic of globalisation and was a prominent member of the centre-left Social Democratic Party in the Swiss parliament until June 1991.
He was appointed UN Special Rapporteur on the Right to Food in 2000.
Ziegler is one of several top Swiss UN representatives, including special adivisor for sport Adolf Ogi and human rights expert Walter Kälin.