The rush for biofuels could harm the world's poorest people, Oxfam has said.
In a new report, the UK aid charity appears to be joining a growing chorus of concern about the side-effects of Europe's drive to get fuel from plants.
The European Union wants to cut the CO2 emissions from burning fossil fuels and has demanded that 10% of all transport fuels should come from plants by 2020.
But Oxfam warns poor farmers risk being forced off their land as industrial farmers cash in on the biofuel bonanza.
Its report says to meet the rise in demand, the EU will have to import biofuels made from crops like sugar cane and palm oil from developing countries.
The rush by big companies and governments in Indonesia, Colombia, Brazil, Tanzania and Malaysia to win a slice of the "EU biofuel pie" threatens to force poor people from their land, it adds.
This could destroy their livelihoods, lead to the exploitation of workers and hit food availability and prices, says the report.
It is now demanding the EU reviews its biofuel policy and wants safeguards put in place to protect the poor.
The European Commission says it is working to make sure its biofuel policy does not backfire.
The BBC's environment analyst Roger Harrabin said there were also fears over the environmental cost of making fuel from crops like maize.
Scientists have said it takes so much energy to produce some biofuels that it would be cleaner overall to burn petrol in our cars, he said.
To make it worse, he added, valuable rainforest is still being cleared to make way for fuel crops like palm oil.
Robert Bailey, a policy advisor at Oxfam, said: "In the scramble to supply the EU and the rest of the world with biofuels, poor people are getting trampled.
"The EU proposals will exacerbate the problem. It is unacceptable that poor people in developing countries should bear the cost of questionable attempts to cut emissions in Europe.
"Biofuels are not a panacea - even if the EU is able to reach the 10% target sustainably, and Oxfam doubts that it can, it will only shave a few per cent of emissions off a continually growing total," he said.
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