Campaigners for a tax on financial transactions urged David Cameron to follow the lead of president Francois Hollande as he introduced a 0.2% levy on share trading in France.
The French tax, which came into effect yesterday, is expected to raise €500m (£390m) next year and is a precursor to a wider European tax, which Britain is not expected to join.
The tax will be imposed on share purchases involving publicly-traded businesses with a market value over €1bn (£787m) and Mr Hollande has indicated that some of the revenue will be used to fight global poverty and HIV/Aids.
Advocates of the tax say that it will also help curb the speculation which has been blamed for contributing towards the financial crash of 2008.
Mr Cameron and Chancellor George Osborne has said Britain will only consider getting involved in a financial transaction tax (FTT) - known to campaigners as the Robin Hood Tax - if it is imposed across the whole world, to avoid damaging the City.
In May, the Prime Minister told other European Union leaders an FTT would cost jobs and put up the price of insurance and pensions: "It will make Europe less competitive and I will fight it all the way," he said.
David Hillman, a spokesman for the Robin Hood Tax campaign, said: "It's great news that France is forging ahead with a Robin Hood Tax - showing it's capable of putting the interests of people before the profits of a privileged few.
"Europe's biggest economies are making the banks pay their fair share for the damage they've caused - the UK Government could do the same but instead chooses to protect their friends in the City."