Alistair Darling pledged today that the government would step up its fight for a new international tax on banking despite an initially frosty response to the plan from Washington.

The chancellor said there was broad agreement among Britain's partners in the G20 group of rich and developing nations that it was worth exploring new curbs on global finance following the worst economic crisis since the 1930s.

After Gordon Brown's unexpected weekend backing for consideration of a so-called Tobin tax, Britain now plans to keep up the pressure ahead of an International Monetary Fund report on transaction taxes, due out in April.