After a battle with cancer, former Council of Trade Unions (CTU) president Helen Kelly has died, aged 52.
"She was a remarkable woman and a wonderful leader," current CTU president Richard Wagstaff says.
"I think many of us feel we've been robbed."
Ms Kelly was diagnosed with terminal lung cancer in February 2015. She was initially given about seven weeks to live.
"She was a wonderful person to work beside and she gave me a lot of support and encouragement, so we'll all miss her very dearly," Mr Wagstaff told Paul Henry.
"She was a special person and you don't come across someone like that often, if ever."
Sonya Rockhouse, whose son died in the Pike River mining tragedy, said her last time with Ms Kelly was difficult.
"[It was] probably the hardest day for us to have to say goodbye, because by the time we left, she had deteriorated over that week. We knew that it would be the last time…"
Former Labour Party president Mike Williams told Paul Henry even though the sad news was expected, it was still a shock.
"We had a long time to get used to the idea, but frankly I'm shattered by the news."
He said she'll be remembered best for helping get better safety in the workplace, "particularly in forestry industry. She worked very, very hard there, and the number of deaths in that industry has plummeted as a result of her work."
"Moreover she was the future of the Labour Party in many ways," he said.
"She expressed to me many years ago her intention to go into Parliament, and I would've welcomed that. This has sadly been taken away from us."
Mr Wagstaff said Ms Kelly was a great political person with "a very incisive mind".
"...and a real sense of justice and fairness, and it drove her to take on anyone and anything if she thought it was wrong.
"I think she would have made her presence felt in a big way if she had remained with us. She seemed to be growing in her presence and her influence," he said.
Her legacy will be a much more positive view of the trade union movement by the media and the general public, Mr Williams said.
"She certainly could not be characterised as some sort of left-wing ogre, she was always reasonable."
Ms Kelly was New Zealand's leading campaigner for medical cannabis. She recently returned from the United States with medical marijuana, something she believed was crucial to her living "pain-free."
Ms Kelly was the daughter of well-known trade unionist Pat Kelly. She began working as a primary school teacher, where she became involved in teacher unions.
"Helen worked with the West Coast community for justice ever since 29 miners were needlessly killed at Pike River. She campaigned to stop the reckless abuses of safety laws and implement best practices," the CTU said in a statement.
"Helen fought for a better working life for all, especially those who found it hard to make ends meet. Her principled stance empowered people in the film industry to speak up together with one clear voice for a fair return on their work."
Tributes from New Zealand leaders are pouring in on social media.