London - The era of "cheap oil" is definitely over and prices could again soar, to as much as 200 dollars per barrel, the International Energy Agency (IEA) warned Wednesday.

"One thing is certain. While market imbalances will feed volatility, the era of cheap oil is over," said IEA Executive Director Nobuo Tanaka in London Wednesday.

The IEA's World Energy Outlook 2008, presented in London, said the oil price could soon be back up to 100 dollars a barrel from the current level of around 50 dollars.

A lack of investment, rather than a shortage of global resources, posed the greatest risk to supply at present, the IEA said.

The report's authors predict that massive investments in energy infrastructure will be needed, and put their estimate at 26 trillion dollars up to 2030.

A significant amount of that money - 8.4 trillion dollars - would need to be spent on oil and gas exploration and development.

The IEA estimates that current resources would be sufficient to supply the world for a further 40 years at present rates of consumption.

In one scenario considered by the IEA, China and India will account for just over half of the increase in world primary energy demand between 2006 and 2030, and much of the increase in world oil demand.

The report also contains a stark warning of the consequences of continuing to rely on fossil fuels, and said the need to improve energy efficiency should not be hampered by the credit crunch.

It described the consequences of political inaction on the issue of climate change as "shocking" and called for strong, coordinated action to curb the growth in greenhouse gas emissions and the resulting rise in global temperatures, it said.

"We must usher in a global energy revolution by improving energy efficiency and increasing the deployment of low-carbon energy," Tanaka said. (dpa)