Speaking on Radio 4's Today programme, Professor Robert Watson expressed alarm at the government's plans to introduce compulsory quotas for use of biofuels in petrol and diesel, calling for the effects of biofuels on food production and their contribution to deforestation to be considered.
"It would obviously be insane if we had a policy to try and reduce greenhouse gas emissions through the use of biofuels that actually leads to an increase in the greenhouse gases from biofuels," he said.
Watson's comments echo those of the government's chief scientific advisor, John Beddington, who expressed concerns over the impact of biofuels on world agriculture in a speech at Westminster earlier this month. The large-scale conversion to biofuels in the US is thought to be one of the main factors that has contributed to the sharp rise in animal feed prices, which is crippling pig and poultry farmers across the globe.
Beddington added that cutting down rainforests to grow biofuels was "profoundly stupid". At this year's MLC Outlook conference, climate expert Tara Garnett explained that deforestation would lead to carbon sequestration, which would negate the positive benefits of biofuels.
"We have to consider not just the direct impacts, but the secondary impacts. For example, the production of biofuels led to deforestation and the carbon stored in those trees will then be released into the atmosphere," she said.
The government has committed the UK to ensuring that at least 2.5% of petrol and diesel for vehicles come from biofuels by 1 April, rising to 5% by 2010. The quotas are designed to ensure that Britain complies with an EU directive, which states that 5.75% of petrol and diesel must come from renewable sources by 2010.