20/01/2008 (Guardian Unlimited) - Controversial plans to make cars greener by using fuel made from crops and animal fat will be thrown into doubt this week when MPs are expected to question whether they will do more harm than good.

Biofuels have been hailed as a green alternative to oil by some, but in the US, where there are massive plants converting maize (corn), it has been criticised for making food more expensive and being environmentally unfriendly.

From April, petrol and diesel sold in the UK must have 2.5 per cent biofuels, drawn from sources such as tallow, rapeseed and sugar beet, rising to 5 per cent in two years' time. The EU wants to increase this to 10 per cent by 2020.

But the House of Commons Environmental Audit Committee is likely to call tomorrow for the schemes to be delayed because of fears that biofuels can have negative consequences. Criticisms include claims that producing some biofuels emits more greenhouse gases than fossil fuels and that habitats such as tropical rainforests are being destroyed to plant the new crops. The report, 'Are Biofuels Sustainable?', is also thought to predict that rising food prices pushed up by competition for land could restrict growth in the industry.

The committee's report follows a separate study last week by the Royal Society calling for strict controls on how biofuels are grown. Stavros Dimas, the EU Environment Commissioner, has also admitted that it might have been premature to press ahead with biofuels, which were fiercely debated at the United Nation's Bali conference on climate change in December.

Groups representing farmers and biofuel producers have warned any delay could damage the fledgling industry at a time of intense competition from overseas. Clare Wenner, head of transport biofuels for the Renewable Energy Association, said: 'The US won't close down [their industry], Brazil isn't going to close down, EU countries aren't going to close down, the emerging countries are not going to close down and the world is not going to have the example we have set because we won't be there.'

Phil Woolas, the UK Environment Minister, said he had not seen the report, but defended the government's plans, particularly the requirement that in two years' time biofuels must cut greenhouse gas emissions by a minimum amount. 'Even if biofuels are not as good as people claim, the question that matters is, are they better than oil?' he said. 'The answer in most cases is they are.' However, any moratorium would be welcomed by campaigners, who claim Britain and other countries have rushed into biofuels. Friends of the Earth, which said it could not comment on the report, is concerned that there is not enough distinction between good and bad biofuels and believes there are better alternatives. Hannah Griffiths, FoE's biofuels campaigner, said: 'We should be pushing for more efficient engines, smaller vehicles and better public transport so people want to drive less.'

Britain produces about 55,000 tonnes a year of bioethanol, which is added to petrol, mostly from sugarbeet, and 75,000 tonnes of biodiesel, added to diesel, from tallow and rape, soya and palm oil. Two million tonnes a year would be needed to meet the 5 per cent target.