LONDON (Reuters) - A “silent tsunami” unleashed by costlier food threatens 100 million people, the United Nations said on Tuesday, and aid groups said producers would make things worse if they curbed exports.

Rice is displayed for sale at a whole-sale food market in Hanoi April 5, 2008. REUTERS/Kham

Prime Minister Gordon Brown said Britain would seek changes to EU biofuels targets if it was shown that planting crops for fuel was driving up food prices -- a day after the bloc stood by its plans to boost biofuel use.

The World Food Programme (WFP), whose head Josette Sheeran took part in a meeting of experts Brown called on Tuesday to discuss the crisis, said a “silent tsunami” threatened to plunge more than 100 million people on every continent into hunger.

“This is the new face of hunger -- the millions of people who were not in the urgent hunger category six months ago but now are,” she said ahead of the meeting.

Riots in poor Asian and African countries have followed steep rises in food prices caused by many factors -- dearer fuel, bad weather, rising disposable incomes boosting demand and the conversion of land to grow crops for biofuel.

Rice from Thailand, the world’s top exporter, has more than doubled in price this year. Major food exporters including Indonesia, Kazakhstan, Egypt and Cambodia have imposed curbs on food exports to secure supplies.

Sheeran said artificially created shortages aggravated the problem: “The world has been consuming more than it has been producing for the past three years, so stocks have been drawn down.”

Rising prices meant the WFP was running short of money to buy food for its programs and had already curtailed school feeding plans in Tajikistan, Kenya and Cambodia.

Sheeran said the WFP, which last year estimated it would need $2.9 billion in 2008 to cover its needs, now calculated it would have to raise that figure by a quarter because of the surge in prices of staples like wheat, maize and rice.

END OF AN ERA

Britain pledged $900 million to help the WFP alleviate immediate problems and Brown raised further doubts about the wisdom of using crops to help produce fuel.

“If our UK review shows that we need to change our approach, we will also push for change in EU biofuels targets,” he said a day after the EU stood by its target of getting a tenth of road transport fuel from crops and agricultural waste by 2020.

Japanese Agriculture Minister Masatoshi Wakabayashi said Tokyo would propose the World Trade Organisation set clear rules for food export restrictions imposed by producer countries.

Tokyo wanted a WTO mechanism for food importers such as Japan to be able to give an opinion when notified about restrictions by an exporting country, Wakabayashi said, according to the text of a news conference published on the ministry’s website.

Rajat Nag, managing director general of the Asian Development Bank, said the era of cheap food was over and urged Asian governments not to distort markets with export curbs but use fiscal measures to help the poor.

U.N. Secretary-General Ban Ki-moon has said dearer food risked wiping out progress on cutting poverty.

His predecessor Kofi Annan said climate change was aggravating the global food crisis and many poor countries could be facing the start of “major hunger disasters”.

“The poor are bearing the brunt and they contributed the least to climate change. The polluter must pay,” he said. “Climate change is an all-encompassing threat -- a threat to our health, security, political stability and social cohesion.”