The former general secretary of Unison Rodney Bickerstaffe has died at the age of 72.
Alan Cummings, secretary of the Durham Miners’ Association, said its members were deeply saddened at the passing of Mr Bickerstaffe, a man they called "a giant of the Labour movement."
Mr Cummings added: "Rodney was always a great friend ours and a great supporter of the Durham Miners’ Gala, speaking many times from the platform at the Big Meeting.
"He was a great personal friend of our late general secretary Dave Hopper and late president Dave Guy.
"Rodney and his union gave the NUM huge moral and financial support during the strike and we’ll never forget his solidarity.
"The trade union movement has lost a giant.
"Our thoughts on this sad day are with Pat and the family and Rodney's very many friends."
The tribute has been posted on the association's Facebook page, alongside a photo of Mr Bickerstaffe standing alongside Dennis Skinner at the Gala.
Mr Bickerstaffe led the public sector union NUPE before it merged to become Unison.
Unison general secretary Dave Prentis said: "Rodney, or Bick as he was known to many, was a great personal friend to many of us and a dedicated champion of all the union members he proudly represented throughout his career.
"He coupled a great sense of humour and love of laughter with a deep-rooted sense of social justice and commitment to Unison.
"Our thoughts are with Rodney's family, especially his wife Pat who was an ever present support to him in all his work and was the love of his life.
"At the time of Rodney's death, it is worth reflecting on his response during the Winter of Discontent to the question 'what about the dignity of the dead?' Rodney replied 'what about the dignity of the living?'
"We at Unison hold this truth close and we will continue Rodney's fight to ensure dignity for our members, our families and all in our communities.
"I'm sure many of us recall the powerful speeches and advocacy he provided to deliver these goals. Rodney was at his best when he was fighting for the causes he believed in, and our movement has today lost one of the greatest campaigners and orators of his generation.
"Everyone involved in our union will share in the grief felt at Rodney's passing. He was a friend, a comrade and a leader, and thanks to his work the lives of countless people have been changed for the better.
"Rodney was the very best of us, a true giant of our movement and we will all miss him greatly."
Labour leader Jeremy Corbyn, who worked with Mr Bickerstaffe when they were both officials in NUPE, said: "He was a warm, decent and principled man, an outstanding trade unionist and socialist, and a great friend and support to me over many years.
"He played a huge role in the labour movement - as a leader of low-paid workers, as founding general secretary of Unison and as a tireless champion of the minimum wage.
"Rodney always provided guidance to me as an MP and was a loud and important voice in all debates within the party. He stood steadfast for Labour principles.
"Rodney was always global in his views and perspectives, a real internationalist.
"I last saw Rodney just before Labour Party conference and was deeply moved by the love for him shown by all the staff, from all over the world, at University College Hospital. Despite his pain and sadness at his condition, he was full of optimism and hope."
Mr Bickerstaffe replaced Jack Jones, the Transport and General Workers Union leader, as the president of the National Pensioners Convention (NPC) in 2001 and served for four years.
Jan Shortt, NPC general secretary, said: "Rodney was a passionate advocate for Britain's older people, and often took on the Labour government over issues which he felt were wrong such as the refusal to restore the link between the state pension and earnings, and the way in which social care was means-tested.
"He was extremely funny and filled the room with his enthusiasm for life. He often used to begin his speeches by saying that when he started as a young trade union official, he turned up to a refuse collectors dispute with a brand new brief case and was met with laughter when he told the workers his name was Rodney.
"In later years, he used to say 'I don't care what they call us, so long as we get a decent state pension'.
"He was one of the labour movement's greats and the NPC is proud to have had the benefit of his skills, intellect and humour."
Unite general secretary Len McCluskey said: "The union movement has lost one of its 'greats' today.
"Rodney was renowned for his warmth and encouragement towards young activists building the foundation of future leadership.
"From us all Rodney, thank you for all your service, your commitment to our values and your friendship. Our thoughts are with Rodney's family and union friends."
TUC general secretary Frances O'Grady said: "Not every union leader can say they were loved, but Rodney was loved by everyone.
"He was a very warm and charismatic leader, with an amazing ability to remember everybody's name regardless of job or rank.
"Rodney will be remembered as a great champion for equality and social justice, especially for low-paid women.
"He was the powerhouse behind the introduction of the national minimum wage.
"Rodney was a pillar of the TUC general council and our movement."
Former prime minister Tony Blair said: "Rodney was a giant of the Labour and trade union movement, one of the most influential trade unionists of his time and of any time.
"He should be remembered not only for his great service to his members, but for his contribution to Britain, not least the seminal role he played in bringing about the introduction of the national minimum wage.
"Where we had our disagreements, he was firm but always friendly and knew at a profound level the importance of having a Labour government. He had a great sense of humour, no pretensions despite his success and was wonderful company."