Helen Kelly was a "relentless changemaker" who made New Zealand a better place, her former colleagues say.
Kelly, the former head of the Council of Trade Unions (CTU), died this morning in Wellington after a battle with lung cancer.
Former Labour Prime Minister and head of the United Nations Development Programme Helen Clark said she was "deeply saddened" by news of Kelly's death.
"Helen was a lifelong and very effective advocate for workers' rights," Clark said.
"She has fought a very challenging illness with the courage which has characterised her entire life, and continued her advocacy for others even while very ill.
"Helen was a truly remarkable person, and will be greatly missed. I offer my deepest condolences to her family and her very large community of friends."
Political leaders pay tribute
Prime Minister John Key tweeted this morning: "Saddened to hear about the passing of Helen Kelly, a strong advocate for workers' rights.
"My thoughts are with her family and friends."
Labour Party leader Andrew Little said Kelly had fought for New Zealanders to have a "safe and decent working life".
"Helen was a fighter. She was a passionate advocate for the causes she believed in - fair treatment for working people, justice in the workplace and the opportunity for all Kiwis to live better, more fulfilling lives at work."
Kelly continued to stand up for what she believed in even after being diagnosed with cancer, he said.
"To the very end of her life, she was an example of extraordinary dedication and tenacity."
Workplace Relations and Safety Minister Michael Woodhouse acknowledged Kelly's work after the Pike River disaster, in which 29 coal miners were killed.
"She championed the cause of making our workplaces healthier and safer," he said.
Woodhouse said he enjoyed their robust and respectful discussions, and he admired her passionate advocacy for her causes.
Green Party co-leader Metiria Turei said Helen was "an exceptional New Zealander" and a "force to be reckoned with".
"She was the kind of person that you'd want in your corner, no matter the fight.
"Even at the end of her life, she was working to make New Zealand better. She was, and will always be, an inspiration."
Working class champion
Council of Trade Unions president Richard Wagstaff said 52-year-old Kelly had died too young.
She would "always be remembered in our hearts, minds and on the front lines of the fight for everyday working people", he said.
"When people were killed at work in the forestry sector Helen was there as a compassionate friend and relentless changemaker. She succeeded.
"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.
"Her death is such a loss to all of us here at the CTU and throughout the union movement."
You get to a stage when we're fighting for an issue - where do you turn to next? And she always knew where to turn.
Pike River Families spokesman Bernie Monk said Kelly's death was a big loss for his group, and for the country.
"We've notified the families this morning because it's a really sad day for us.
"When Pike River actually happened, she was on our doorstep the first day. And she never left our doorstep."
Kelly had been assisting two of the victims' families in a new court case against the Department of Labour.
"She was a straight-shooter, honest, and passionate about where she was going.
"It was in all industries, not just Pike River - the film industry, the forestry industry, fishing, anything."
Kelly was able to "make things happen" when it appeared their efforts for justice were at a dead end.
"You get to a stage when we're fighting for an issue - where do you turn to next? And she always knew where to turn."
BusinessNZ chief executive Kirk Hope said his organisation had worked with Kelly on many issues over the years.
He said she would be remembered "as a fierce champion of worker rights", but also as someone with warmth "and sometimes mischievous humour".
Grey Mayor Tony Kokshoorn, who also worked with Kelly during the Pike River mine disaster said she was always helping grieving families and would go to the memorials every year.
"She had an unbelievable temperament, her personality was second to none and she always showed great concern for others that really puts her out in front."
In her honour, the families of Pike River miners and forestry workers killed on the job set up a support group for other families.
Fellow medicinal cannabis supporter Huhana Hickey said Helen Kelly was a compassionate person who kept fighting for people until her last breath.
"I just immediately felt the sadness that our whole country is going to feel, she dedicated her life to people, she dedicated her life to the workers.
"She dedicated her life to change and social justice, we haven't got leaders like that in large numbers here and we're going to lose a significant voice in this country," she said.
Dr Hickey said Kelly advocated for people because she cared about struggling people.
E tu union national secretary Bill Newson said Kelly was "a visionary and an inspiration".
"Her legendary leadership, fierce determination and brilliant ideas will have an everlasting impact on workers in Aotearoa."
He paid tribute to Kelly's fearless passion for workers' rights, particularly after the Pike River tragedy.
"The families of the men whose lives were taken that day are deeply thankful for the love, compassion and support that Helen gave.
"What Helen built will continue. How she faced and fought her last and greatest campaign will live in our collective union memory forever," Newson said.
The Human Rights Commission said New Zealand lost someone whose work was felt by "thousands of New Zealanders".
Equal Employment Commissoner Dr Jackie Blue said Kelly "[embodied] what it means to be a human rights advocate".
New Zealand Nurses Organisation's Cee Payne and Glenda Alexander said: "A totara has fallen and the crash in the forest is reverberating in the union movement. We have one less but we believe there are other seedlings growing strong to make the New Zealand workplace a fair and respectful environment. Rest in peace Helen."
Employers and Manufacturers Association chief executive Kim Campbell said although he was often on the other side of the argument, "we had deep respect for Helen and her work".
"New Zealand has lost a powerful advocate for social justice," said Campbell.
Meat Workers Union national secretary Graham Cooke said: "She lent so much hope and inspiration to us and to the union movement. Her death is an incredible sorrow, but she has passed her fighting spirit on to all of us."
Public Service Association national secretaries Glenn Barclay and Erin Polaczuk said: "To the very end, she was campaigning for the causes she believed in - and thinking about how the union movement would continue to survive and thrive after she was no longer here to champion it."
Federated Farmers president William Rolleston said Kelly "put forward rational and empathetic arguments which were often hard to disagree with no matter what end of the political spectrum you came from. We have lost a great New Zealander."
Post Primary Teachers' Association president Angela Roberts said Kelly was "our union rock".
"Helen never gave up fighting for working people from every sector - whether they be education staff battling for better working conditions, or saving the lives of forestry workers by advocating for improved health and safety protections. Helen dedicated her entire career to improving the working lives of others."
Association of Salaried Medical Specialists executive director Ian Powell said Kelly's death was an "enormous loss".
"She was known as a determined, generous and kind person who remained, until the end, a strong voice for change," Powell said.
Set for bigger things
Labour Party President Nigel Haworth said Kelly had dealt with her crippling illness with "irrepressible fortitude and humour".
She was determined that her final months should make a difference for others, he said.
Haworth said Kelly had an ability to see the big picture in the day-to-day life of people, and was able to translate their struggles into political campaigns and policy.
"Nowhere is this more obvious than in her health and safety work around, for example, Pike River and the forestry sector.
"It was also true in her final days as she campaigned on the medicinal cannabis issue."
The Labour president also spoke about what she might have achieved had she not succumbed to cancer.
It was no secret that Kelly might have entered Parliament one day, he said, and some saw her as a future Labour leader.
She could have also taken up senior roles in the international labour movement.
"Leaving her CTU role was to be the start of another chapter in the life's work for working people.
"This is not to be, and we lament the arbitrary extinguishing of such potential for good."