Roses and 'groovy tunes' greet Prime Minister Jacinda Ardern

Jacinda Ardern's mother, Laurell, was missing from her swearing-in as Prime Minister yesterday because she was attending the birth of her second grandchild.

Ardern's sister, Louise, gave birth to a boy in London.

Ardern was sworn in at Government House by Governor-General Dame Patsy Reddy in a ceremony attended by Ardern's partner, Clarke Gayford, and her father, Ross, New Zealand High Commissioner to Niue.

Ardern told a boisterous crowd at Parliament afterwards that she would lead a strong, empathetic and inclusive Government that should be judged on how it treated the most vulnerable.

Among the welcome party at Parliament was a band of four calling themselves Stardust Stompers, who wanted to support the new Government with some "groovy tunes", said frontman Joe Lindsay, a member of Fat Freddy's Drop. "I think she's great, and I think it's gonna be great for New Zealand."

Deborah Read, from Otaki, brought two red roses - one for Ardern and one for Winston Peters. She had told Peters on his Facebook page to choose Labour, and she was glad he had followed her advice because they complemented each other well.

Loud cheers erupted when Ardern stepped out of a bus, followed by her ministers and under-secretaries.

She joked that it was great to have "roughly one-eighth of the band Fat Freddy's Drop" playing at what amounted to a public inauguration.

It was "an enormous privilege and an honour" to serve New Zealand, she told the crowd. "We take incredibly seriously the roles and responsibilities that we have adopted today.

"Not everyone voted for us ... But we vow that regardless of who you voted for, regardless of where in Aotearoa New Zealand you live, this will be a Government for all New Zealanders. We will be an active Government. We will be a strong Government. We will be an empathetic Government. And we will be a Government that works together."

Ardern said New Zealand was a wonderful place "that can be even better", where everyone deserved decent wages, world-class healthcare and education, and a healthy environment.

"We are a society that should be judged by how we look after our most vulnerable."

She said the Government had a lot to do. "And we cannot do it alone ... We will work with the business communities, we will work with NGOs and community organisations, we'll work with Maori ... we will work together. And that work begins today," she said.

"There will be good days and there will be bad days, but no matter what, we will always remember the vote that you gave us, the vote of support, and the debt of gratitude that we owe you.

Ardern walked along the front of the forecourt, greeting supporters.

She then embraced Gayford and his two nieces and, hand in hand, they walked up the steps to Parliament House.