Far from being the salvation of an oil-hungry society, biofuels could actually trigger increases in food prices and deforestation, according to a report.

It doesn't suggest doing away with them altogether, but says that current targets for swapping petrol and diesel for fuel derived from crops are too ambitious.

The UK government, and the European Union have set their sights on using biofuels in 10 per cent of our cars by 2020. But the Co-op's report suggests that to produce this amount of fuel on a global scale would require as much as nine per cent of arable land being diverted to fuel crops.

Professor Dieter Helm, who sits of the government's Council for Science and Technology, told the BBC: "The sort of targets being set for biofuels will have quite radical effects on agriculture and therefore will have very substantial consequences for food prices and agriculture more generally."

He points out that rainforest is already being felled to make way for fuel crops.

"Think of the energy involved in felling those rainforests. Think about the damage to the climate being done by the loss of those trees. Think about the ploughing and the cultivation of fields. Think about the transport of those fuels, and you start to realize the carbon imprints are about much more than simply what happens to grow in a particular field at a particular point in time."