Global food prices have hit "dangerous levels" that could contribute to political instability, push millions of people into poverty and raise the cost of groceries, according to a new report from the World Bank.

The bank released a report Tuesday that said global food prices have jumped 29 percent in the past year, and are just 3 percent below the all-time peak hit in 2008. Bank President Robert Zoellick said the rising prices have hit people hardest in the developing world because they spend as much as half their income on food.

"Food prices are the key and major challenge facing many developing countries today," Zoellick said. The World Bank estimates higher prices for corn, wheat and oil have pushed 44 million people into extreme poverty since last June.

The report comes a day before Finance ministers and central bank chiefs from the Group of 20 leading economies meet in Paris. Zoellick said he's worried some countries might react to food inflation by banning exports or implementing price controls, which would just aggravate the problem.

The World Bank's food price index rose by 15 percent between October and January alone. The increase has been driven by volatile global trading in wheat, corn and soybeans. Global corn futures more than doubled since this summer, from $3.50 to $7 a bushel, in part because of higher demand from developing countries and a growing biofuels industry.

Prices are rising in part because global grain traders have gotten jittery about historically low reserve levels of corn, wheat and soybeans, said Chris Nagel, an analyst with Northstar Commodity in Minneapolis. Growing demand from customers in China and elsewhere is putting pressure on the supply of most commodities, he said.

The U.S. Department of Agriculture predicted last week U.S. corn farmers will have just 675 million bushels of corn at the end of August, before next year's harvest begins. That's just an 18-day supply, Nagel said.

The slim reserves mean traders will likely bid up crop prices further at any weather event that reduces next year's planting.

"We need to get good crops, all around the world, in all of these commodities," Nagel said. "You just don't have much foot room for error.

The global price of fats and oils rose 22 percent and wheat rose 20 percent between October and January, according to the World Bank. The prices of sugar rose by 20 percent in that time.

Industrialized nations like the United States are insulated from the price increases because raw ingredients account for just a fraction of the total food costs. But in many developing counties, prices get transmitted more drastically.

Between June and December, wheat prices climbed 54 percent in Kyrgyzstan, 45 percent in Bangladesh and 16 percent in Pakistan, for example.

Zoellick warned that higher prices could stoke political instability in countries like Egypt and Tunisia. Both countries are big wheat importers and higher grain costs could aggravate social unrest as the countries form new regimes, he said.

"That's where the international system needs to try to be aware of these issues, and try to do things at a minimum not to exacerbate food prices," he said.