The law increasing the amount of biofuel that must be included in petrol and diesel up to a minimum of 2.5% has come into force in the UK.
The Government heralded the move as a way to allow motorists to be “able to fill their tanks with greener fuels”.
However, as soon as it came into force on April 15, critics said the new law will do more harm than good.
Environmental campaign group, Greenpeace, said the new rules will “drive rainforest destruction and could actually accelerate global warming”.
Senior forests campaigner Belinda Fletcher explained: "Right now, rainforests are being destroyed to make way for biofuel crops in places like Indonesia.
"This destruction leads to massive greenhouse gas emissions and completely undermines the point of these so called green fuels.”
The RSPB and Oxfam have also voiced their concerns about the new law.
“Some biofuel production will cause habitat loss, displace food production and emit more greenhouse gases than are being saved,” warned Graham Wynne, RSPB chief executive.
Oxfam called the new law “reckless” pointing out that there are also links between biofuel production and human rights abuses, slave labour, and rising global food prices.
Despite the growing evidence against biofuel use, the Government pushed ahead and introduced the law as part of its Renewable Transport Fuel Obligation (RTFO).
This obligation should see all road fuels sold here contain 5% of biofuel by 2010, which will bring the UK in line with European legislation.
However, motorists can still avoid putting biofuel into their vehicles.
In a move that was supposed to protect suppliers against fluctuations in biofuel prices, the Government has allowed fuel suppliers the option to pay a 'buy out' price in respect of some or all of their biofuel obligation.
A Department for Transport (DfT) spokesman confirmed that a fuel supplier can buy its way out of having to add biofuels to its fuel.
The DfT could not say yet whether any fuel supplier had yet taken this decision.
In defence of the new law, which is predicted by the Government to save 2.5 million tonnes of carbon dioxide by 2010, a DfT spokesman said: “The UK has gone further than any other country to give fuel suppliers a real incentive to produce sustainable biofuels that do not harm the environment.
"Suppliers are required to produce sustainability reports including information on where their biofuel crops come from and the level of carbon savings they will achieve.”
But Greenpeace pointed out that the reporting process is not robust enough.
“Suppliers are only required to "report" the details of the crops they are using - a process which can be easily manipulated to hide the true origin of environmentally damaging crops like palm oil,” said a spokesman.
Government ministers rallied to support the law amid the growing criticism.
"Emissions from transport need to go down if we are to make serious headway in tackling dangerous climate change and this initiative has the potential to deliver considerable carbon savings,” Phil Woolas, minister for the environment said.
“Obviously sustainability needs to be at the heart of all biofuel production.
"We must be able to produce biofuel without causing a negative impact on our natural environment."
Transport minister Jim Fitzpatrick added: "We must do all we can to ensure biofuels are produced sustainability.
"We know people are concerned about the environmental risks associated with expanding biofuel production and we take those concerns very seriously."