02 April, 2009 - Published 16:13 GMT
Caribbean and other offshore financial centres have been given an ultimatum by leaders of the world's largest economies - sign up to information sharing or be named and shamed.
Giving the closing remarks at the end of the G20 Summit in London, the British Prime Minister Gordon Brown said action would be taken against tax havens that did not comply with new standards of transparency.
Mr Brown said the banking secrecy of the past must come to an end.
"We've agreed that there will be an end to tax havens that do not transfer information on request.
The banking secrecy of the past must come to an end."
Speaking on behalf of the G20, Mr Brown announced that a list of non-compliant tax havens was being published "where action must immediately be taken".
“We have agreed tough standards and sanctions for use against those who don't come into line in the future,” he declared.