One of the world's biggest tax havens, Switzerland, has agreed on request to hand over the secret bank account details of Australians, in a hit to money laundering and international tax fraud.

The revised tax treaty, signed by Assistant Treasurer David Bradbury on Tuesday, will contain information exchange rules to allow for data held by Swiss banks and financial institutions to be shared with Australian tax authorities with few questions asked. It is the first time the government has changed the treaty since it was established over three decades ago.

It is a major step towards filling in the blanks. Credit:Bloomberg

The revised treaty comes at a time when tax authorities in Britain, the US and Australia are grappling with a huge cache of secret offshore data leaked to the International Consortium of Investigative Journalists earlier in the year. The data revealed the activities of dozens of accountants, lawyers and financial advisers who have assisted in the establishment of companies in tax havens.

While tax experts warn the revised treaty could have gone further to include automatic information exchange - the new standard set by the Organisation for Economic Co-operation and Development - they say it is still a landmark step in countering Switzerland's long-entrenched bank secrecy rules. Those exposed will be rich Australians as well as criminals, they say.