Leading climate change expert Nicholas Stern pressed G20 leaders Monday to grasp the opportunity to forge a green recovery from the economic slump.

World leaders should focus on promoting environmentally sustainable growth when they meet in London, said Stern, the author of a key climate change report and a former World Bank chief economist,

"This is an opportunity to have a green recovery that lays the foundations of growth for the next two to three decades," Stern said at the launch of his new book "Blueprint for a Safer Planet".

He added: "Let us organise our emergence from the crisis by investing in the short-term projects, such as energy efficiency, which can generate demand and employment quickly and by bringing forward some of the energy and transport infrastructure investments which can lay the foundations for medium- and long-term growth."

Stern urged the leaders of the Group of 20 developed and developing economies meeting in London Thursday to send a strong signal that there was a pressing need "to get on with" drawing up a global deal on climate change.

An international conference will be held in Copenhagen in December to draw up a new agreement on greenhouse gases.

"We've got a good chance of getting an agreement in Copenhagen -- but it's quite possible for the world to make a mess of this," he said.

Stern also insisted it was wrong to say that the overriding priority was to deal with the current economic crisis and postpone action on climate change. This idea "should be confronted", he said.

His 2006 Stern Review has become the benchmark for calculating the economic cost of tackling climate change.