Pop queen Madonna got 70,000 jumping up and down for action on climate change in the finale to the London leg of Live Earth.

"If you want to save the planet I want you to start jumping up and down," she told the packed Wembley Stadium. "Come on mother f***ers, if you want to save the planet let me see you jump."

The singer opened her set with a song especially written for the anti-global warming event billed as the "greatest show on earth".

The London show was one of 12 held worldwide on all seven continents - including Antarctica.

In total, more than 150 of the world's most popular music acts joined former US Vice President Al Gore's campaign to "heal the planet".

Organisers claimed up to two billion people watched the concerts in cities including Washington, Sydney, Rio De Janeiro, Johannesburg, Tokyo, Shanghai and Hamburg.

In the British capital, Madonna was joined on stage by the Red Hot Chili Peppers, the Black Eyed Peas, James Blunt, The Foo Fighters, Kasabian and the reformed group Genesis featuring Phil Collins.

Duran Duran aptly opened their set with the song Planet Earth. "Everyone who did not arrive on a private jet put your hands in the air," said lead singer Simon Le Bon, who also raised his hand.

But critics have raised questions about whether Live Earth can do anything more than boost the profile of the stars taking part.

Bands like the Arctic Monkeys have stayed away, saying it is hypocritical for jet-setting acts with higher than average carbon footprints to illuminate the problem of global warming.

But speaking from the Washington concert, Mr Gore called on the developed world to reduce carbon emissions by 90%.

"Not many years from now, our children and grandchildren will ask one of two questions, looking back at us in 2007," he said via video link.

"Either they will ask 'What were they thinking, didn't they hear the scientists, see the evidence, didn't they care, or were they too busy?'

"Or they will ask the second question, which I prefer. I want them to ask of us: 'How did they get their act together to successfully solve the climate crisis?'"

Sharon Looremeta, a Kenyan Masai woman, pressed home the message when she took to the stage.

"I'm here today to tell you that my people are already suffering from the terrible effects of the changing climate, making our survival even more difficult," she said.

Organisers said the power used for the Wembley concert was sourced from renewable energy.

The audience were urged to recycle their plastic water bottles and cups in bins at the stadium.

Yet at the end, thousands of plastic cups lay on the stadium floor.