Biofuels could produce twice the carbon emissions of the fossil fuels they replace, environmentalists have claimed.

Friends of the Earth said rules introduced a year ago which require a certain percentage of UK transport fuels to be made up of the “green” fuels could, instead of cutting emissions, have created an extra 1.3 million tonnes of CO2.

The emissions could have come from the “indirect” impacts of biofuels, for example the cutting down of forests for food production which had been displaced from land turned to growing crops to make ethanol or biodiesel.

But supporters of biofuels said that in the first year of the Renewable Transport Fuels Obligation (RTFO), the industry had shown it was possible to produce sustainable fuels in the UK.

The Renewable Energy Association also warned against the government’s policy of slowing down the planned increases in the levels of biofuels in the fuel supply over concerns about their impact.

This is because it must meet an EU target of 10 per cent renewables in transport by 2020.

And the REA criticised the rules brought in on reporting how sustainable biofuels are – because they allow companies to say the origins and sustainability of the fuels are “unknown”.

A year on from the introduction of the fuels obligation, the amount of biofuels required in fuels has risen from 2.5 per cent to 3.3 per cent, a smaller increase than originally planned following concerns over their effects.

Friends of the Earth claimed that rather than reducing climate change emissions, the RTFO could be producing the equivalent emissions to putting an extra half a million cars on the road.

The environmental group’s executive director Andy Atkins said: “One year on, it’s clear the biofuels obligation is a failure. Investing in first class public transport is a much better way to reduce emissions on our roads.”

But Clare Wenner, of the REA, said: “We really have been able to demonstrate that UK biofuels can make the grade on carbon savings and being produced sustainably.

“It can be done and we are doing it, in the face of competition from Brazil and everywhere else.”

But she said a mistake in the drafting of the rules, which reduced the amount of biofuels actually needed in the system, had been an “absolute disaster” for the industry, pushing UK businesses to the wall and leading to job losses.