The Electoral Commission has refused to register Hannah Tamaki's political party Coalition New Zealand because the name could create confusion.
A spokesperson for the commission said the word 'coalition' had a specific meaning - a grouping or alliance of multiple parties.
Under MMP, governments were usually coalitions and it was common to refer to the government as "the coalition", the spokesperson said.
The commission decided the name Coalition New Zealand could confuse voters, as they could believe they were voting for a grouping of other parties, or that they were voting for a party associated with the government.
It said the party could reapply for registration with a different name and logo.
The leader of Coalition New Zealand, Ms Tamaki, responding to the rejection, said it had been a "fabulous practice run".
"Wait for the real thing, exciting days ahead," she said.