KiwiSaver will increase inequality and benefit the wealthy, according to research done at Waikato University.
More than 380,000 people have joined KiwiSaver to take advantage of tax breaks and a $1000 kick-start payment.
Professor John Gibson of the university's management school said NZ Super helped to "equalise lifetime incomes" but KiwiSaver did the opposite.
"What's having the biggest impact [on inequality] is the generous taxpayer incentives provided to KiwiSaver members and in particular the exemption from withholding tax."
He said because these were not capped, higher earners received more benefit. "Non-earners and the self-employed don't benefit at all."
According to Professor Gibson's research, more than 45 per cent of the working-age population earn below $30,000, but they will get just 15 per cent of KiwiSaver tax incentives.
The 11 per cent of the working-age population who earn more than $70,000 will receive 18 per cent of KiwiSaver tax incentives.
Women, Maori, Pacific Islanders and those without qualifications will get a much smaller share than white, educated males, he said. "You have to ask if that is a fair use of taxpayers' money."
Professor Gibson also said KiwiSaver had not inspired new saving but rather a "reshuffling" of existing savings.
The research was based on a mail survey last month. About 1600 surveys were sent out and 598 completed and returned.