Maori Party co-leader Tariana Turia says she will step down at the next election.
Turia, who has signalled her intention to retire previously before changing her mind, said she would have spent 18 years in Parliament by the time she leaves in 2014.
The Maori Party said Turia had signalled her intention to leave early so it could prepare for her departure and put a succession plan in place.
"I have given it serious thought and have made the decision with my family not to seek re-election in 2014," Turia said.
Her co-leader Pita Sharples said it would be a "huge change to lose my mate".
Turia would not give up her roles as minister and co-leader in the interim.
A minister in the former Labour government, Turia set up the Maori Party after quitting in protest at Labour's contentious Foreshore and Seabed Act.
She won her Te Tai Haururu seat in a by-election.
Turia has been the lynch pin of the Maori Party's success and has a large personal following.
Her departure may see the party struggle to win representation in 2014.