Five Pacific countries have been named by the European Union as being "non-cooperative" tax havens.
The list of 30 territories includes the Cook Islands, Nauru, Niue, Marshall Islands and Vanuatu.
Hong Kong, Brunei and a number of Caribbean tax havens were also named as part of a crackdown on multinational companies who avoid paying tax in the EU.
At a press conference EU Economic Affairs Commissioner Pierre Moscovici said the blacklist was intended to "push non-cooperative non EU jurisdictions to be more cooperative and adopt international standards".
Two years ago the Cook Islands was named in what was claimed to be the biggest financial leak in history - millions of documents were released exposing the identities of politicians, celebrities and business people out to avoid paying tax.
Cook Islands authorities reacted quickly to defend its offshore finance business which is a big money earner for the country's economy - second only to tourism.
The Cook Islands Financial Supervisory Commission said its authorities have gone to a great deal of trouble to improve its international standing.