The government's biofuels policy is unsustainable and unethical, Oxfam has said.
The global charity is holding a protest in Westminster today against the renewable transport fuel obligation, which from tomorrow will force all diesel and petrol sold in Britain to contain 2.5 per cent of biofuels.
World Bank chief Robert Zoellick has warned rising food prices in the last three years put 100 million people at risk of being pushed into poverty and Oxfam believes the development of biofuels is contributing to the problem.
It is probing reports that land-grabbing is taking place in many developing countries around the world for the development of biofuel plantations and that human rights are being breached as a result.
Oxfam adds there is "growing scientific evidence" that biofuels are exacerbating global warming trends, rather than helping reduce the problem.
And it blames the government for committing itself to the biofuel obligation without properly establishing the consequences of biofuels as a result.
"It is outrageous that the government is forcing compulsory use of biofuels onto the British public without full evidence of their impact," Oxfam policy adviser Robert Bailey said.
"It's like treating a patient with an untested medicine that could make them even more unwell."
Organisations like Biofuelwatch and the Royal Society for the Protection of Birds are also opposed to the obligation, but the National Farmers' Union (NFU) says biofuels are sustainable.
"We must make sure that the biofuels which we do engage in are sustainable, they get their carbon footprint right and they make real, deliverable, sustainable changes," NFU president Peter Kendall said.
The Department for Transport said it was important to ensure biofuels were sustainable.
A spokesperson said they would reduce the impact of transport on the environment and that the obligation's gradual introduction would cut carbon emissions by around 2.5 million tonnes a year.
"This means the UK has gone further than any other country to address the sustainability impacts of biofuels and we will not support any increase in biofuel targets beyond five per cent until effective standards are in place," he added.