The prices of staple foods will more than double in 20 years unless world leaders take action to reform the global food system, Oxfam has warned.
By 2030, the average cost of key crops will increase by between 120% and 180%, the charity forecasts.
Half of that increase will be caused by climate change, Oxfam predicts, in its report Growing a Better Future.
It calls on world leaders to improve regulation of food markets and invest in a global climate fund.
"The food system must be overhauled if we are to overcome the increasingly pressing challenges of climate change, spiralling food prices and the scarcity of land, water and energy," said Barbara Stocking, Oxfam's chief executive.
Women and children
In its report, Oxfam highlights four "food insecurity hotspots", areas which are already struggling to feed their citizens.
in Guatemala, 865,000 people are at risk of food insecurity, due to a lack of state investment in smallholder farmers, who are highly dependent on imported food, the charity says.
in India, people spend more than twice the proportion of their income on food than UK residents - paying the equivalent of £10 for a litre of milk and £6 for a kilo of rice.
in Azerbaijan, wheat production fell 33% last year due to poor weather, forcing the country to import grains from Russia and Kazakhstan. Food prices were 20% higher in December 2010 than the same month in 2009.
in East Africa, eight million people currently face chronic food shortages due to drought, with women and children among the hardest hit.
The World Bank has also warned that rising food prices are pushing millions of people into extreme poverty.
In April, it said food prices were 36% above levels of a year ago, driven by problems in the Middle East and North Africa.
Oxfam wants nations to agree new rules to govern food markets, to ensure the poor do not go hungry.
It said world leaders must:
increase transparency in commodities markets and regulate futures markets
scale up food reserves
end policies promoting biofuels
invest in smallholder farmers, especially women
"We are sleepwalking towards an avoidable age of crisis," said Ms Stocking.
"One in seven people on the planet go hungry every day despite the fact that the world is capable of feeding everyone."
Among the many factors driving rising food prices in the coming decades, Oxfam predicts that climate change will have the most serious impact.
Ahead of the UN climate summit in South Africa in December, it calls on world leaders to launch a global climate fund, "so that people can protect themselves from the impacts of climate change and are better equipped to grow the food they need".