The world faces "a permanent oil shock" and will have to adjust to sustained high prices in the next two decades, the International Monetary Fund said on Thursday in the starkest official warning yet about the long-term outlook for energy supplies.

Predicting surging demand from emerging countries and limited new supplies from outside the Organisation of the Petroleum Exporting Countries after 2010, Raghuram Rajan, IMF chief economist, said: "We should expect to live with high oil prices."

"Oil prices will continue to present a serious risk to the global economy," he added.