Philanthropy: Please can I have £500,000 cashback?

She is a glamorous socialite and former model. He is a Nobel Prize-winning economist. It would be foolish, however, to dismiss them with a cliché about beauty and brains: together, they are going to save the world, starting with Africa.

Their plan is simple, if ambitious: Renu Mehta and Sir James Mirrlees will gather the world’s super-rich together on 3 March at the Dorchester, in central London, and begin the process of shaking billions of dollars out of them. It will be the most ambitious and audacious fundraising plan the world has seen since Bob Geldolf’s Band Aid, and at its core is a simple cashback plan.

The scheme, which has the support of United Nations Secretary-General Ban Ki-moon, is the brainchild of the Cambridge economist Sir James Mirrlees, and is simple. Ms Mehta and Sir James hope to persuade the G8 governments to return 50 per cent of any private donation in the form of tax breaks, and then make up the difference from their own aid budgets.

So, if a wealthy Russian oligarch were to give $1m – some £700,000 – to the scheme, they would receive $500,000 back. The difference would be made up from government money already earmarked for overseas aid.

About 100 of the world’s richest people – each worth $1bn or more – will assemble at the Dorchester to be entertained by the singer Joss Stone and lectured by the CNN founder Ted Turner, who, in 1997, announced that he was donating $1bn to UN causes. Carol Vorderman will host proceedings while the supermodel Milla Jovovich will introduce the best-selling author Paulo Coelho.

The beauty of the plan, Ms Mehta says, is that governments such as Britain’s have pledged to donate 0.7 per cent of their GDP to aid, but are way off the target. This will help them to meet their commitments without costing them extra. Her ultimate aim is to raise $75bn.

In the past three years, Ms Mehta has made the transformation from self-confessed spoilt It-girl to one of the world’s leading philanthropists. The speed dials on her mobile phone include the rich and powerful, from Tony Blair to Bill Clinton. Her Fortune Forum, which she founded in 2006, helps a new stratum of global society – the “super-rich” – to shed excess wealth by passing it on to worthy causes. The event at the Dorchester will be its third annual summit.

The daughter of Vijay Mehta, an Indian textile magnate, now wants to resolve the chronic problems facing Africa – such as disease, including Aids, famine, and lack of education. “We’ve already had a couple of meetings with the British Treasury,” Ms Mehta said this weekend. “We’ve pitched it and we’re still in talks. The scheme will operate for all income brackets. But I founded the Fortune Forum with the super-rich in mind. The richest 1 per cent own 32 per cent of the world’s wealth and the inequity is widening.

“The genius of this proposal is that it doesn’t cost the taxpayer anything. Half a billion people in the world are living on less than a dollar a day and millions live without clean water. It’s despicable. But I realised it will take billions to resolve these problems.”

Sir James Mirrlees added: “It seems to me a simple and compelling idea. It adds an incentive for people to give.”