One billion people throughout the world suffer from hunger, a figure which has increased by 100 million because of the global financial crisis, says the UN.
The UN's Food and Agriculture Organisation (FAO) said the figure was a record high.
Persistently high food prices have also contributed to the hunger crisis.
The director general of the FAO said the level of hunger, one-sixth of the world's population, posed a "serious risk" to world peace and security.
The UN said almost all of the world's undernourished live in developing countries, with the most, some 642 million people, living in the Asia-Pacific region.
In sub-Saharan Africa, the next worst-hit region, the figure stands at 265 million.
Just 15 million people are left hungry in the developed world.
"The silent hunger crisis - affecting one-sixth of all of humanity - poses a serious risk for world peace and security," said Jacques Diouf.
"We urgently need to forge a broad consensus on the total and rapid eradication of hunger in the world and to take the necessary actions."