Finance ministers of the G20 countries have given tax havens until March 2010 to tackle tax evasion, or face harsh sanctions.
Representatives of the world's largest economies have threatened offshore centres on the OECD list of "tax havens" with sanctions, unless they increase transparency.
Ministers asked the Financial Stability Board of G20 central bankers, finance ministry officials and regulators to report on compliance and criteria by 2009, according to reports by Reuters.
The G20 will then by ready to use countermeasures against tax havens from March 2010.
In April, G20 leaders agreed to name and shame the world's tax havens identified on the OECD list of "white" and "grey" jurisdictions. Sanctions were also threatened but no time scale was set.
The list comprises "white list" jurisdictions which have implemented international standards in tax information sharing, and "grey list" centres, which have agreed to the measures but have not enforced them yet.
G20's move to crack down on tax evasion comes as Germany was paying for data of Liechtenstein's bank clients and the US was embroiled in a dispute with UBS, which it accused of aiding wealthy Americans dodge tax.
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