Tax Justice Aotearoa has started a public campaign in support of a capital gains tax. It is a coalition of various trade unions, churches and community groups.
Its reason for being is described in this passage:
Tax Justice Aotearoa NZ seeks a fairer society through tax reform. We represent the growing number of people who wish to see greater transparency, equality and fairness in national and global tax systems. Founded in August 2018 and linked with the global Tax Justice Network, we provide analysis, ideas and information to create an informed dialogue about how tax builds societies where all people flourish.
There is a petition that you can sign.