The Labour Party says it won't rule out extending a new capital gains tax to the sale of a family business or farm.
Its finance spokesperson, Grant Robertson, said it was unfair that property speculators could make profits buying and selling without being taxed.
Labour has ruled out taxing the sale of the family home, but, speaking on TVNZ's Q + A, Mr Robertson wouldn't rule out taxing other family concerns.
"What we want to do is to address the fact that we've got a huge imbalance in our tax system between hardworking people who go to work every day and pay their taxes and people who are speculating in the property market who don't ... what we're not prepared to do is shy away from hard issues."
Labour is formally launching its election campaign in Auckland this afternoon.