Ngarewa-Packer is a former deputy mayor of South Taranaki. She was first elected to the South Taranaki District Council in the 2007 local elections, representing the Pātea ward, having also unsuccessfully contested the mayoralty. However, new mayor Ross Dunlop named her as his deputy mayor. She held that role until 2010, when she did not seek re-election and was replaced by Alex Ballantyne.
Māori Party
Ngarewa-Packer was elected co-leader of the Māori Party in April 2020, along with John Tamihere. Both ran uncontested. She had previously been selected to be the Māori Party's candidate for the Te Tai Hauāuru electorate for the 2020 election in October 2019, and was the first electoral candidate announced by the party for that election. Ngarewa-Packer and Tamihere are the first party leaders elected since the Māori Party lost its parliament seats in the 2017 election, after which its previous leaders stepped down.
Ngāti Ruanui and local activism
Ngarewa-Packer is chief executive of the Ngāti Ruanui iwi. She is also kaiarataki of Te Rūnanga o Ngāti Ruanui, which runs healthcare centres in Hāwera and Pātea. Ngarewa-Packer has been advocating for Māori health and the environment at a grassroots level for many years. She has campaigned against iron sands mining off the Taranaki coast. In April 2020, the Court of Appeal found that the Environmental Protection Authority's decision in 2017 to grant a marine discharge consent to a mining company was not consistent with the law to protect the environment from harmful substances. However, the company behind the plan is seeking leave from the Supreme Court to appeal. On the appeal, Ngarewa-Packer said "We’re annoyed that we may have to go to court for a fourth time as right now our efforts are focused on protecting our community from Covid-19. But we are undeterred in our resolve and we will oppose TTR’s application for yet another appeal." In 2004, she rallied more than 250 Taranaki people to join with the foreshore and seabed hikoi on its way to Wellington. In 2011, she joined a 10-member independent panel set up by the Government to identify ways to raise the rate of return on Maori-owned assets, and grow Maori contribution to New Zealand's economy. Regarding the Covid-19 response, The Spinoff described Ngarewa-Packer as "a key voice in the Covid-19 iwi response, not only in analysing and mitigating risks in her own rohe, but in keeping applied pressure on local and central government to include Māori in their risk assessment."
Personal
Ngarewa-Packer is of Ngāti Ruahine, Ngāruahine, and Ngā Rauru iwi. She is a descendant of Tutange Waionui of Ngati Ruanui, who fought alongside Titokowaru during the New Zealand Land Wars and claimed credit for killing Austrian mercenary Gustav Von Tempsky. Ngarewa-Packer was a nominee for the Taranaki Daily Newsperson of the year in 2018.