Mr Robertson said at his campaign launch today that if successful, he would be recommending Ardern to the Labour caucus as his deputy.
"She connects with a broad range of New Zealanders, lives and breathes our values and has driven bold and new policy for children. I would be proud to serve with her."
"We must harness all the talents of the Labour team to win in 2017," Mr Robertson said.
"As a caucus and party we need to come together around clear and direct policies that are true to our values. We can not expect New Zealanders to back a party that is not unified and clear in our purpose. We must leave behind our differences and earn the trust of our people by our actions from here.
"My commitment is that under my leadership Labour will once again be the vehicle for the hopes and aspirations of a broad range of New Zealanders and that we will face the future with pride and confidence."
Mr Robertson said Ms Ardern could speak to all New Zealanders.
He joked she also had the best knowledge of whiskey of anyone in the party.
Ardern said she and Mr Robertson joined the Labour Party about the same time in 1997.
"Grant is my colleague, but first and foremost, Grant is my friend."
'We've got to be talking to New Zealanders'
Appearing on TVNZ's Q&A this morning, Mr Robertson said Labour needed to review all of its policies and be clear and true to the party's values.
"There's a group of New Zealanders who feel that we're not speaking to them about their lives. They're all sorts of people from different backgrounds."
"What we've got to be talking to New Zealanders about is what kind of New Zealand they want to be a part of.
"Work's changed and we've got to get alongside the courier drivers and the people who are starting the new small businesses and say to them, 'we back you as well'," Mr Robertson said.
"We've got to have clear policies that speak to people's lives. When we do that, we'll come together around that.
"If people step outside of it, there have to be consequences."
David Parker said politics was a mixture of people, policy and presentation. "We got that mix wrong obviously."
"New Zealanders are not going to come back to Labour until they've got confidence in us. For them to have confidence in us we have to express our unifying purpose across the party that they agree with which serves their purpose.
"For me, that's taking Labour party primarily back to the interests of working New Zealanders.
"We were a party born of working people for working people and I think that people look at the Labour party now and they see that we're more there for the vulnerable primarily now.
"I think that the way to protect the vulnerable is to actually take working New Zealanders with you
Too many people at the election were ashamed to admit that they were voting Labour, Mr Parker said. He said he would lead by looking outwards, not inwards.
Nanaia Mahuta said some of Labour's policies, including a capital gains tax, no longer spoke to the broader constituency of working people.
Labour needed to use its diversity and skill-set from across its caucus to ensure the party was focussed its core objectives, she said.
Andrew Little said New Zealanders were looking to politicians to find solutions to their problems.
"They didn't hear solutions from us to their problems.
"I think people are wanting an environment where we've come out of difficult economic circumstances. We know people are struggling.
"They wanted to hear something that was going to give them a bit of stability, a bit of confidence about the future and that's not what they heard from us.
"My general summary is that we put a lot of things out there that in the end, scared a lot of people off," Mr Little said.
"If we as the Labour party care about ensuring there is a fair society, less inequality, dealing with child poverty, we need to be in government.
"We put a bunch of our things out there asking people to vote for us that turned people off us. We've got to be honest about that."
