Mana and the Internet Party will confirm an alliance tomorrow to contest September's election.
It is understood the two parties have reached an agreement which will see a new, combined grouping unveiled to contest the election, though the two organisations will remain separate outside Parliament.
Hone Harawira is expected to be named the leader of the new party. He will also remain the leader of Mana.
The decision also suggests Kim Dotcom's Internet Party has finally selected a leader, as Mana had said any agreement would depend on the chosen candidate.
The two parties have been in discussions over an election agreement for several weeks.
Internet Party chief executive Vikram Kumar and Harawira are to reveal the outcome tomorrow.
"The negotiations for Mana have involved a number of important considerations from policy to personnel, and of course, liaison with Mana branches and members up and down the country. We've now completed the process and come to a clear majority decision,’’ Harawira said.
The talks between the parties have centered on the Internet Party's choice of leader as well as on policy agreements.
Harawira has cited Dotcom's resources and internet savvy as reasons for the merger. Dotcom this month donated $250,000 to the party he founded.
The Internet Party, polling at about 1 per cent, hopes to enter Parliament on Harawira's coat tails should he hold onto his Te Tai Tokerau seat.
While the agreement has ultimately found favour, some Mana members, such as former Green Party MP Sue Bradford, have threatened to leave.
Is it time for Judith Collins to go?Related story: Judith Collins looking isolated