Prime Minister Jacinda Ardern has arrived at Ratana Pa, fronting on last night's agreement over the revised Trans Pacific Partnership before the brass band marched her and her entourage to the marae for a powhiri.

Labour and Ratana have an historic alliance going back to the 1930s when prophet Tahupotiki Wiremu Ratana signed an agreement with Michael Joseph Savage.

Ardern is the first Labour Prime Minister to attend the annual celebration of the birthday of Ratana Church founder Tahupotiki Wiremu Ratana since Helen Clark.

This year is the 100th anniversary.

Ardern arrived on a bus with other Labour MPs and the Green Party. Coalition partners NZ First arrived separately, but all three parties were welcomed together as a Government grouping.

National will be welcomed this afternoon, in a break from the past few years when all political parties have been welcomed on in one group.

Ardern will head to Waitangi next week in the lead-up to Waitangi Day, opting to spend five days in the north rather than the usual two.

Ardern has been granted speaking rights on the marae at Waitangi for the welcome, years after her predecessor Helen Clark was driven to tears because her right to speak was objected to.

It is protocol on many marae for women not to speak.

Ardern said she felt honoured to be offered it. She said she had made it clear that she was happy to follow marae protocol "and whatever decision was made I would happily follow that decision".

She said she had wanted the decision to come from the marae.

The powhiri will be held on the upper marae at the Treaty grounds this year rather than Te Tii after successive tensions at the lower marae around the attendance of politicians and media.