The UK Government must drop its drive for biofuels or British motorists will face paying up to £2bn extra at the pump per year by 2020, ActionAid UK and Friends of the Earth have warned.
Both also claim that the policy could create carbon emissions equivalent to six million extra cars on our roads while having disastrous consequences for people's lives in developing countries.
New research commissioned by the charities, undertaken by the International Institute for Sustainable Development, shows that Government plans to increase the proportion of biofuels in UK petrol to meet our share of the EU's renewable energy target will increase the cost of fuel by the equivalent of an additional litre on every full tank.
As well as hitting consumers' pockets hard, biofuels are bad for business - by 2020, a typical UK lorry driver will be spending as much as £1,400 extra per year on diesel.
The plans could also create an extra 13 million tonnes of carbon emissions every year in the UK while more people in developing countries go hungry and are pushed off their land as biofuel crops are grown instead of food.
The European Union's Renewable Energy Directive, which requires 10 per cent of all energy used in EU transport to come from renewable sources by 2020, promotes biofuels as a greener alternative to fossil fuels.
But research by the charities shows that the reality is quite the opposite; rather than cutting greenhouse gas emissions most biofuels increase them.
Meredith Alexander, ActionAid UK's head of policy, said: "The UK must scrap its biofuel targets. Motorists, the environment and poor people in developing countries will bear the brunt of this ill-conceived directive.
“Prices at the pump will be higher and so will CO2 emissions. Increased biofuel production will have disastrous consequences as food prices are forced up and millions of people go hungry and lose their land."
Kenneth Richter, Friends of the Earth's biofuels campaigner, said: "The Government keeps talking about bringing down costs but here we are paying billions for biofuels that do nothing to boost our economy and nothing to tackle climate change.
"This money would be better spent on improving our train and bus services, promoting cleaner cars, and making cycling a much safer option for short journeys - saving people cash every day."