Robust investment of $3 trillion into five key sectors, including renewable energy and sustainable transport, could help revive the global economy and boost employment while accelerating the fight against climate change and poverty, says the United Nations.

The policy brief for a Global Green New Deal, developed by economists and the UN ahead of the G-20 meeting of world leaders in London in early April, highlights the benefits of investing a significant amount of the $3 trillion-worth of global stimulus packages in five areas.

The UN Environment Programme said these areas include raising the energy efficiency of old and new buildings, more emphasis on renewable energy sources.

The three other areas are sustainable transport including hybrid vehicles, high-speed rail and bus rapid transit systems; the planet's ecological infrastructure, including freshwaters, forests, soils and coral reefs; and sustainable agriculture, including organic production.

"The G-20 meeting needs to be a milestone in terms of focusing investments that address the crises of today and those emerging from climate change, natural resource scarcity and lack of decent employment for close to 2 billion unemployed or underemployed people over the coming decade," UNEP executive director Achim Steiner said.