Microsoft billionaire Bill Gates has given a boost to supporters of a Robin Hood Tax by telling the G20 summit that such a levy on financial transactions was "clearly technically feasible".
In a report to the Group of 20 leading economies, Mr Gates said it was "critical" that a portion of the money raised from any Financial Transaction Tax (FTT) should be used to help the developing world, rather than simply to shore up ailing First World economies.
An FTT - which this week won the backing of the Archbishop of Canterbury was one of a range of measures which Mr Gates said could bring the number of the world's poor states down to "zero".
Britain has said it supports the idea of an FTT in principle, but only if it can be introduced globally. Prime Minister David Cameron warned earlier this week that demands for its introduction may be used as a smokescreen by countries keen to draw attention away from their failure to live up to existing commitments on aid.
French President Nicolas Sarkozy, who commissioned the Gates Report for today's summit, is a strong supporter of a European Commission proposal for an EU-wide levy on transactions and has spoken out against British and American reluctance to sign up to a levy.
It is understood he was critical of the UK's role in blocking progress towards an EU FTT when he spoke to aid charity representatives. But Save the Children director of policy Brendan Cox said it was "slightly rich" of the French to blame Britain when - unlike Paris - the UK is on track to meet its pledges on aid.
Mr Cox said it was vital that the row over the FTT did not get in the way of G20 states taking up some of the wide-ranging proposals in Mr Gates' report.
The computer geek-turned-philanthropist said that a "paramount" role in the fight against poverty would be played by technological innovation in areas such as agriculture and vaccines.
And he said that G20 countries could also help by measures including legally-binding transparency requirements on mining and oil companies, a reduction in costs of remittances sent home by migrant workers, imposing a "solidarity" tax on tobacco to fund healthcare in the poor world or diverting a portion of taxes raised on shipping and aviation fuel.
Warning donor governments against cutbacks in aid in response to domestic financial pressures, Mr Gates said: "Leadership from the G20 is critically important right now."