Andrew Little has not ruled out tax increases if Labour is elected to Government in 2017.
Mr Little told The Nation programme, Labour has no plans to raise taxes at the moment but the issue would be reviewed if the party gets voted in.
"You get the resources of the Government and you can actually lead a debate with people, rather than the kind of half measures that this Government tends to promote."
Mr Little added there would need to be support from the New Zealand electorate.
"We won't make any material change to the tax system without going to the people first"
Labour's potential support partners, the Greens and New Zealand First, both believe the tax system should be adjusted.
Green Party Finance spokesperson Julie Anne Genter told Newshub her party campaigned on raising the top income tax bracket so those who earn over $140,000 will pay seven cents extra on each dollar.
"It's just important our tax system is simple and fair, and it is fair for those on the highest incomes to give a little more back."
Ms Genter added while the Greens will review this policy she doesn't expect major changes.
NZ First leader and Northland MP Winston Peters said the tax system should be more targeted.
"The tax regime in this country [needs] to seriously incentivise investment in our provincial economies in particular."
In the 2014 election campaign National promised income tax cuts beginning in April 2017.