Young people under the age of 18 should have been allowed to vote in the country's flag referendum, a youth group leader says.
The postal vote starts tomorrow.
Youthtown chief executive Paula Kearns said young New Zealanders were often the most engaged on significant issues.
"It is young people who are very interested in the future of their country, and this decision has huge significance for them," she said.
"This is the flag under which they will live most of their lives as New Zealanders."