The idea of taxing transactions between banks and financial institutions to raise funds for global issues like poverty and climate change was floated by Gordon Brown at a G7 finance ministers meeting last November.
Dubbed the "Robin Hood tax", it was immediately dismissed by the United States and Canada but it has been reported that the British prime minister has high hopes it will be accepted by the IMF in April.
Leading economist Jeffrey Sachs, who is in London to speak in support of the tax, spoke to Stephen Sackur.
You can watch the full interview on Wednesday 10th March 2010 on BBC World News at 04:30, 09:30, 15:30, 21:30 GMT.
And on the BBC News Channel at 04:30 and 23:30.