"We had a meeting last night, and unanimous support for her," he said.
"The Māori caucus has taken into account the great work that she has done in terms of our strategies and going forward, so there's a heck of a lot of support there."
Whaitiri, who holds the Māori electorate of Ikaroa-Rāwhiti, said she had a lot of work to do on behalf of her constituents.
"I just want to get on with it," she said.
Jackson said there was no reason why Whaitiri could not be a "strong and good MP for Ikaroa-Rāwhiti and a leader for our caucus".
He would not say what discussions the caucus had had with the Prime Minister's decision.
"The discussions with the Prime Minister remain private. We support her decision and we support our colleague continuing in a leadership position."
Ardern said last Thursday that she no longer had confidence in Whaitiri as a minister after receiving a report into an incident in Gisborne on August 27 between Whaitiri and a staff member.
Whaitiri was suspended as Customs Minister on August 30. The details of the incident have never been revealed but it is believed there was a physical altercation between Whaitiri and a press secretary who had been in the job for only a week.
"While the facts are in dispute, the report says an incident occurred. Meka Whaitiri continues to contest details of the incident, but there are elements which are agreed," Ardern said.
Whaitiri would not say today which parts of the report she disputed.
"I can't talk about the report until it's released, but like I say, I accept the Prime Minister's decision. It's been a debilitating time but I really want to reflect on what I need to do to improve myself."
She would not say whether she had apologised to the staff member involved.
She said she was humbled by the support of the Māori caucus.
Ardern said on Thursday that she still had confidence in Whaitiri as an MP and left the door open for a return to Cabinet.
"I have a view that the member works incredibly hard across Ikaroa-Rāwhiti, that she will continue to be able to fulfil those roles. However, based on what I have seen, I do not have confidence in her retaining her role as minister," Ardern said.
Whaitiri lost the portfolios of Customs, Associate Agriculture, Associate Crown Maori Relations, Associate Forestry and Associate Local Government.
She said today it was not her decision whether she might one day return to Cabinet.
