The world must take care when developing biofuels to avoid perverse environmental effects and higher food prices, Nobel Peace Prize winner and climate change scientist Rajendra Pachauri said.

Speaking at the European Parliament, he questioned whether the US' policy of converting corn (maize) into ethanol for use as a transport fuel would reduce the emission of greenhouse gases blamed for global warming. Controversy has grown over using food crops to make biofuels as an alternative to fossil fuels. Some environmentalists and politicians say it has raised food prices, distorted government budgets and led to deforestation in southeast Asia and Brazil.

"We should be very, very careful about coming up with biofuel solutions that have major impact on production of food grains and may have an implication for overall food security," Dr Pachauri, chairman of the UN's Intergovernmental Panel on Climate Change, told a news conference.

"Questions do arise about what is being done in North America, for instance to convert corn into sugar then into biofuels, into ethanol," he said.

The US is the world's biggest producer of biofuels, derived mostly from corn.

"Several questions have arisen on even the emissions implication of that route, and the fact that this has clearly raised prices of corn," said Dr Pachauri, whose panel shared the Nobel prize with former US Vice President Al Gore last year.

Scientists say some kinds of biofuel generate as much carbon dioxide (CO2) as the fossil fuels they replace.

Supporters, however, say that biofuels are the only renewable alternative to fossil fuels and do generally result in greenhouse gas emission savings.

Dr Pachauri, in Brussels for talks with EU lawmakers, said it was crucial to look at other ways of producing biofuels, including investing strongly in research and development to convert cellulosic material into liquid fuels, as well as using agricultural residues.

EU leaders pledged last year to increase the share of biofuels used in transport, but concern that this is pushing up food prices has led the bloc to say it may reconsider its strategy.

Earlier this month EU leaders pledged to pass laws within 12 months to implement ambitious goals for combating climate change, including slashing greenhouse gas emissions by 20 per cent by 2020 and increasing the share of renewable energy.