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Ardern was the first female prime minister to be given the right to speak at the Northland marae after prolonged discussions. Usually only men are able to speak in powhiri.
She promised to continue meeting with Maori around the country.
"So when we return in one year, in three years, I ask you to ask us what we have done for you.
"Hold us to account. Because one day I want to be able to tell my child that I earned the right to stand here. And only you can tell me when I have done that."
The Prime Minister said they should hold her to account on issues such as child poverty, the environment and prison rates.
It was a peaceful powhiri, watched by about 150 locals and tourists.
Ardern was welcomed on to the upper marae on the Treaty grounds mid-morning after already spending three days in Northland.
She began her speech at the marae at Waitangi with an extended introduction in te reo Maori, using cue cards to ensure it was correct and acknowledged the local iwi and hapu and those who had taken her onto the marae.
"I do not take lightly the privilege extended to me to speak ... today, not only as a Prime Minister but as a wahine."
Ardern also acknowledged her governing parties, NZ First and the Greens.
"As a Government, we have been here for five days. We did not come simply for the beauty and hospitality of the north. We came because there is work to do. And we will only achieve what needs to be done together."
She said those days had canvassed education, health, housing, roads and jobs and now action was required. "This is the beginning for our Government and I thank you."
The Prime Minister said Labour had not created the new ministerial role of iwi-Crown relations lightly.
While some iwi - including Ngapuhi - were yet to settle, the Crown also had to ensure it upheld the terms of the settlements it had signed.
She promised the relationship and responsibility would "continue on with strength and hope."
Family ties to Waitangi
Ardern said her father had brought her and her sister to the Treaty grounds as a child "because he had a great love of history".
She recalled her father handing her the camera to take a photo of her parents there.
"Just as I was about to take the photo he grabbed my mother in the most public display of affection. Kissed her full on the lips just as I was about to take the photo, embarrassing me and my sister immensely."
She said she hoped her own children and others would have memories of the place and learn the history of the Treaty and New Zealand.
"That is our history and we must always be honest about our history and what it means to us."
Ardern said she also hoped they would learn the importance of manaakitanga - of hospitality, generosity and sharing.
"And I hope they know we value the ability to speak frankly and openly with each other. We should never shy away from that because if we don't speak freely as a nation we will never learn."
Ardern also spoke of the problems facing Maori and "the distance between us" - referring to employment and incarceration levels.
"I inherently believe in the power of change. And I hope not only that my child will believe in that too, but that they will see that change."
Earlier this morning the powhiri for Ardern and other MPs began with a series of wero (challenges) for the Government parties.
Ardern's partner, Clarke Gayford, picked up the wero set down for Ardern, a leafy branch laid on the ground by a warrior.
It is customary for only males to take part in the wero, a process to determine whether the visitor is friend or foe.
New Zealand First Leader Winston Peters and Greens co-leader James Shaw also accepted wero.
The parties were greeted with a fierce haka by the warrior waka paddlers.
The National Party has sent a delegation to Waitangi, without leader Bill English.
In 1998, former Labour leader Helen Clark was pushed to tears after there were objections to allowing her to speak on Te Tii Marae.
One of those objecting was Titewhai Harawira, who will this morning escort Ardern in the powhiri, as she has escorted previous Prime Ministers on to Te Tii Marae.
It is one of the few nods to Te Tii Marae, which had the hosting rights removed this year after a series of protests and problems with access for politicians and media.