David Cameron has fought back against accusations that his vision of the Big Society is simply a "cover" for Government spending cuts.

Writing in The Observer, the Prime Minister said that his initiative to hand power to local communities and voluntary organisations was intended to change the way Britain was run.

He acknowledged however that at a time of spending restraint, it would benefit society if people were prepared to volunteer more.

"Building a stronger, bigger society is something we should try and do whether spending is going up or down," he said.

"But there is a broader point to be made. As the state spends less and does less - which would be happening whichever party was in government - there would be a positive benefit if some parts of society were to step forward and do more."

His intervention came after Dame Elisabeth Hoodless - who is standing down as executive director of Community Service Volunteers, Britain's biggest volunteering charity - warned that spending cuts could obliterate the existing volunteer base.

Mr Cameron also dismissed suggestions that the Big Society was too vague a concept to mean anything.

"True, it doesn't follow some grand plan or central design. But that's because the whole approach of building a bigger, stronger, more active society involves something of a revolt against the top down, statist approach of recent years," he said.

"The Big Society is about changing the way our country is run. That's why the Big Society is here to stay."