Bob Geldof has hit out at the series of Live Earth concerts taking place this summer by questioning their motives.

The concerts have been organised by the former US Vice President Al Gore and aim to draw attention to the global warming crisis.

Geldof, however, who organised both Live Aid and Live8, has come forward to criticise Gore, saying that the concerts lack a specific goal.

He told Dutch newspaper De Volkskrant, "I hope they're a success. But why is (Gore) actually organising them? To make us aware of the greenhouse effect?

"Everybody's known about the problem for years. We're all f**king conscious of global warming.

"Live Earth doesn't have a final goal. I would only organise this if I could go on stage and announce concrete environmental measures from the American presidential candidates... They haven't got those guarantees.

"So, it's just an enormous pop concert."