Oxfam said a global system of tax havens allows an estimated total of US$7.6 trillion of individuals' wealth to sit offshore.
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If tax were paid on the income that this wealth generates, an extra US$190 billion would be available to governments every year, the report said.
Oxfam estimated that tax dodging by multinational corporations costs developing countries at least US$100 billion every year. Corporate investment in tax havens almost quadrupled between 2000 and 2014, the report said.
Oxfam New Zealand's advocacy and campaigns director, Dr Jason Myers, said it was hard to know whether New Zealand was suffering from a similar tax dodging situation.
"We just don't know. We do know that in 2013 the Tax Justice Network labelled New Zealand a tax haven for some poor transparencies around foreign tax and registered companies operating here.
"The impacts of the very wealthy individuals and very big companies being able to avoid paying their fair share of tax is that it trickles down to inevitable cuts in essential public services like health and education."
Myers said Oxfam was seeking a global response to the tax-dodging.
"A global system which actually legislated against those very wealthy people hiding their profit would help to alleviate those pressures."
The trend for the gulf to extend suggested the number of 62 people holding the wealth of the poorest half of the population would reduce to 11 by 2020 unless change was implemented.
"It's about a fair system of redistributing income so that we don't see these enormous gulfs between the very, very rich and those who are going without," Myers said.
