President Nicolas Sarkozy of France plans to introduce a tax on financial transactions.
He says the 0.1% tax will come into effect from August.
Mr Sarkozy said on Sunday he hopes to create a shock and inspire other European countries to follow his lead.
In a television interview, Mr Sarkozy said the tax would enable French companies to keep jobs at home instead of outsourcing them abroad.
Advocates of the tax see it as a potentially significant revenue generator as well as a penalty against speculation, but critics say it could cause investors to pull their money out of countries applying it.
Britain is opposed to transaction taxes being implemented across the EU. Germany and Italy advise caution.