London ? Ration cards. Genetically modified crops. The end of pile-it-high, sell-it-cheap supermarkets.

These possible solutions to the first global food crisis since World War II – which the World Food Program says already threatens 20 million of the poorest children – are complex and controversial. And they may not even solve the problem as demand continues to soar.

A “silent tsunami” of hunger is sweeping the world’s most desperate nations, said Josette Sheeran, the WFP’s executive director, speaking Tuesday at a London summit on the crisis.

The skyrocketing cost of food staples, stoked by rising fuel prices, unpredictable weather and demand from India and China, has already sparked sometimes violent protests across the Caribbean, Africa and Asia.

The price of rice has more than doubled in the last five weeks, she said. The World Bank estimates food prices have risen by 83 percent in three years.

“What we are seeing now is affecting more people on every continent,” Sheeran told a news conference.

Hosting talks with Sheeran, lawmakers and experts, British Prime Gordon Brown said the spiraling prices threaten to plunge millions back into poverty and reverse progress on alleviating misery in the developing world.

“Tackling hunger is a moral challenge to each of us and it is also a threat to the political and economic stability of nations,” Brown said.

Malaysia’s embattled prime minister is already under pressure over the price increases and has launched a major rice-growing project. Indonesia’s government needed to revise its annual budget to respond.

Unrest over the food crisis has led to deaths in Cameroon and Haiti, cost Haitian Prime Minister Jacques Edouard Alexis his job, caused hungry textile workers to clash with police in Bangladesh, and stoked protests in Egypt and across Latin America.

Former U.N. Secretary-General Kofi Annan said more protests in other developing nations appear likely. “We are going through a very serious crisis and we are going to see lots of food strikes and demonstrations,” Annan told reporters in Geneva.