The Australian tax authority, the ATO, is seeking details of clients with offshore bank accounts from 57 financial institutions, according to the Australian Financial Review.

The ATO expects to unearth data on 100,000 people with undisclosed offshore income, including capital gains, from July 2005 to June 2009.

Local tax advisor Theo Sakell is quoted as saying: "Overseas tax authorities have been very aggressive in terms of data matching, so it's a surprise that the ATO has taken so long to approach local banks and local branches of foreign banks."

About 500 people have owned up to concealing about A$70 million ($65 million) in overseas income under an amnesty that will end in June 2010, the AFR believes.