The UN's new top adviser on food has urged a freeze on biofuel investment, saying the blind pursuit of the policy is "irresponsible".

Olivier de Schutter also wants curbs on investors whose speculation is, he says, driving food prices higher.

UN officials liken the rise in food prices to a silent tsunami, threatening 100 million of the world's poorest.

The use of food crops for alternative sources of energy like ethanol is one factor behind the price hike.

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Mr de Schutter did not go quite as far as his predecessor in the job, Jean Ziegler, the BBC's Laura Trevelyan reports from New York.

Mr Ziegler had condemned biofuels as a "crime against humanity" and called for an immediate ban on their use.

'Predictable' crisis

But the new special rapporteur on the right to food did insist the American and European goals for biofuel production were unrealistic.

"The ambitious goals for biofuel production set by the United States and the European Union are irresponsible," he said in an interview for France's Le Monde newspaper.

"I am calling for a freeze on all investment in this sector."

The biofuel rush was, he argued, a "scandal that only serves the interests of a tiny lobby".

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