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."
Young people often felt frustrated as they believed their voices weren't heard, Ms Kearns said.
"There may even be a case to consider whether 18 is the appropriate starting age for democratic participation. But certainly on this issue there is a strong case to enable younger New Zealanders to participate."
Youthtown asked 25 of its youth squad members if they wanted to vote. All 25 did: 19 wanted the current flag to stay, four preferred the new flag and two said they wanted an alternative option.
Some squad members saw the flag referendum as a waste of money, while others believed a new flag would be a nice change for the country.