Former Prime Minister Helen Clark has praised her ex deputy Jim Anderton, saying he was a champion for the voiceless and the marginalised.

Anderton, who was deputy prime minister in Clark's government from 1999-2002, died overnight.

"From the very beginning, I knew Jim Anderton as a leader who could inspire others to go the extra mile to get things done and get results," Clark told the Herald.

"In Government he was incredibly hard-working, diligent, was able to relate to a very broad cross-section of New Zealanders, and was always a voice for the voiceless and the marginalised.

"Jim was a very kind person. He hated anybody suffering any sort of injustice at all. He would take up the cause of people who were getting what they were entitled to. He felt very strongly about that.

She said Anderton came from humble beginnings.

"When he was a child, they were very poor. He knew what it was like to be very poor and he pulled himself up through incredible intelligence and hard work. He was very active in the Catholic workers' movement as a young man and had a strong faith as a young man, and very much informed by the progressive tone of the Vatican in those years. He brought all that background and sense of purpose into his work.

"He was very practical. He was a manufacturer in Auckland, which wasn't a very common experience in the NZ Parliament. So he knew about industry and his contribution to regional and economic development was quite substantial."

Clark said she had known Anderton since the early 1970s.

"We campaigned for seats on the Auckland City Council together. He chaired my selection panel when he became the candidate for Mt Albert. We go back decades."

She said there were difficult times when Anderton left the Labour Party in 1989.

"They weren't easy years. It was a difference within the family, if you like. There were many of us unhappy with the direction of the fourth Labour Government.

"Some chose to stay inside and fight for better times. Jim decided to move outside the party and fight for better times.

"The happiness for me was when it came back together prior to the 1999 election and we campaigned as a team - that was the basis for a very successful Government."

The Labour-Alliance coalition Cabinet, after the 1999 election, headed by Helen Clark and Jim Anderton. Photo / File

Clark said that Kiwibank will be one of his legacies, and admitted she was sceptical about it.

"I was one of the sceptics. How do we know anyone will use this bank? But it was very important part of Jim's policy platform, and the truth was that the major banks had more or less exited so many smaller communities and suburbs. But there was still a post office, so putting Kiwibank into those facilities was a winner.

"It did incredibly well. I was wrong and he was right on that one."

Clark said Anderton's passing was very sad, but not unexpected. She was with Anderton when he was awarded the insignia of a Companion of the New Zealand Order of Merit in September last year.

"Clearly he was well enough to receive it, but he wasn't speaking and he was very frail.

"My sincere condolences to his widow Carole and the family."

Meanwhile Christchurch mayor and former Labour MP Lianne Dalziel said she was "truly saddened" by the news of his death overnight.

"I had the privilege of serving with him in Cabinet and I saw with my own eyes the extraordinary passion he brought to his portfolios. He breathed life into the regions believing as he did in the importance of their success. New Zealand simply could not succeed if the regions did not do well.

"He loved his city of Christchurch with equal passion and he was willing to serve us in so many ways well beyond his retirement from politics. I was pleased he was recognised in the Queens Birthday Honours List last year. It was a real tribute that the Governor-General came to Christchurch for the investiture.

"My sympathies go out to Carole and his family. Your support enabled Jim to serve us all in the way that he did and we are grateful. And to Jim I say thank you on behalf of our city of Christchurch for your dedication and service. May you now Rest In Peace."