The Prime Minister and Labour Party leader went head-to-head in Parliament on Wednesday over whose government was responsible for the disparity in people's incomes.
The Ministry of Social Development has released its Household Incomes Report which measured trends in inequality and hardship from 1982 to 2010.
The report shows the gap between the rich and poor peaked in the early 2000s, then fell from 2004 to 2007 as a result of the Working for Families package.
The gap reduced further by 2010.
Prime Minister John Key argued it shows the distribution of income is more even now than at any time under the previous Labour-led Government.
But Labour leader Phil Goff pointed to evidence in the report that gaps in income between the rich and poor had closed under his party.
The heated session in the House came to a head when Speaker of the House Lockwood Smith threw Finance Minister Bill English out of the debating chamber for talking over him when he was standing.