Prices of agricultural commodity prices are to soar by up to 180% by 2030, unless governments take action to tackle the squeeze on food supplies presented by climate change and a growing world population.
The change in the world weather patterns, reflecting rising levels of greenhouse gases, "will have adverse effects" on both yields and output "across all developing regions", including some of the largest agricultural producing countries, Oxfam said.
"Climate change poses a grave threat to food production," the charity said, citing dangers to underlying yields and of droughts and floods "which can wipe out harvests at a stroke".
Estimates suggested that rice yields may fall by 10% for every rise of 1 degree Celsius in minimum temperatures during growing countries' dry season, with potentially "catastrophic" declines in yields in sub-Saharan Africa.
Corn productivity was poised to fall 35% short of potential in 2030 in South Africa, which remains a significant exporter of the grain, if overtaken by many Latin American countries.
Climate change poses a threat to these countries too, including Brazil, where wheat output will fall 20% below where it would be in 2030.
In rice, China, the world's largest producer, will lose 9% of its potential to the changes in the weather patterns evident in the "climate chaos" which has sent the world "stumbling into our second food price crisis in three years".
With demand increasing with a rise in the world population to 9bn, the impact of unfulfilled supply potential would be evident in prices which, for corn, will soar by nearly 180% by 2030 without government action, Oxfam said.
Rice prises will rise by more than 130%, with those in wheat gaining nearly 120% and livestock prices doubling.
The charity proposed international action to forestall "an avoidable age of crisis", including the shifting of some production from "polluting industrial farms to smaller, more sustainable farms", along with the winding down of subsidies in richer nations.
"Rich country governments have spectacularly failed to resist the capture of agricultural policy making by their farm lobbies," blaming Western subsidies for discouraging agricultural improvements in poorer countries, besides raising taxes in developed nations.