"The concept of energy security is meaningless unless it is seen in the wider context of climate security, where the overriding threat is climate change caused primarily by fossil fuel use," said WWF climate change expert Jennifer Morgan.

The report called for "a serious global 'Climate and Energy Security Plan' similar in dimension to the Marshall Plan", referring to the U.S-led financial aid package for West European countries devastated by World War Two.

The new plan should aim at dramatically increasing energy efficiency to ensure global emissions of CO2 and other climate pollutants peak and decline in the next 10 to 15 years, the Swiss-based WWF said.

The G8 leaders -- from Russia, the United States, Britain, Canada, France, Germany, Italy and Japan -- are due to discuss the future of global energy supplies when they meet in St Petersburg.

"They cannot push their responsibility from one G8 summit to the next -- they have to come up with answers and decisions now," WWF's Morgan said.