Asked to comment on Oxfam's figures yesterday, a spokesman for Finance Minister Bill English said its own reporting showed inequality was not worsening.
"The most comprehensive report on inequality published annually by [the Ministry for Social Development] shows inequality has not got any worse in New Zealand in the past decade."
Billions of dollars a year went to support low-income New Zealanders, the spokesman said, and the tax and income support systems provide significant income redistribution.
This year's Budget provided further measures such as free doctors' visits for children and extended paid parental leave.
"The best contribution the Government can make to support lower income families is to support a growing economy that provides more jobs and higher incomes."
At the invitation of Australia, New Zealand will join a G20 meeting in Melbourne this weekend.
Ms Le Mesurier said the group of nations last year endorsed a plan to address multinational tax dodging, and questioned whether New Zealand had taken enough action on the issue.
In response, Revenue Minister Todd McClay said New Zealand was in a comparatively strong position on such issues compared to many countries.