Australian Labor is mourning the death of Simon Crean, a Labor prince who never became king.
Mr Crean, died in Europe, aged 74, while on a work trip, Prime Minister Anthony Albanese said.
"Simon Crean gave a lifetime of service to his nation, and in particular to the labour movement," Mr Albanese said on Sunday.
Mr Crean will be remembered as one of the architects of the Hawke government's momentous industrial relations reforms of the 1980s and one of the most significant political figures of modern Labor.
He served as a parliamentarian for 23 years, and was a cabinet minister in the governments of Bob Hawke, Paul Keating, Kevin Rudd and Julia Gillard.
"Simon's many achievements in portfolios that ranged from trade to employment, from primary industries and energy to the arts, were characterised by a focus on the national interest, engagement with stakeholders, and always acting with principle and determination," Mr Albanese said.
Mr Crean followed in the footsteps of his father Frank, who served as Treasurer in the Whitlam government and as deputy prime minister in the government's last months.
As ACTU vice-president, Mr Crean played a key role in bringing about The Accord between unions and employers in 1983.
Mr Rudd credited Mr Crean with bringing the industrial relations system kicking and screaming into the 21st century.
ACTU President Michele O'Neil said the former union leader was a great believer in, and fighter for fairness and justice for working people in Australia and around the world.
"He was a leader of conviction and courage and was generous and supportive to young unionists and all those who sought his support and advice," Ms O'Neil said.
Elected to the Victorian seat of Hotham In 1990, Mr Crean became science minister in the Hawke government.
Narrowly missing out on the Labor deputy leadership after Labor's election loss in 1996, he took on the position two years later after another election defeat.
After a third consecutive defeat in November 2001 he was elected unopposed as leader.
Mr Crean faced continued speculation about a Kim Beazley comeback amid poor opinion poll results and in November 2003 he resigned on the advice of colleagues - becoming the first Labor leader since 1916 to be replaced without having contested an election.
Former prime minister Julia Gillard said Mr Crean dedicated his life to Labor values.
"He hated injustice and fought hard to bring opportunity to all," Ms Gillard said in a statement.
"He took his work seriously but was also caring, sociable and fun."
Deputy Prime Minister Tanya Plibersek remembered him as: "Smart, principled, courageous and kind."
Mr Albanese said Mr Crean was a "great servant of the Labor party and of the broader labour movement" and above all was thoroughly decent and kind.
"This brought him respect across the political spectrum," he said.
The former leader of the federal Labor parliamentary party was "a gentleman", Opposition Leader Peter Dutton said.
"I always admired Simon for his intellect and decency... A very sad day," he tweeted.
Former prime minister Tony Abbott paid tribute to "a thoroughly admirable man".
"He never made the mistake of identifying the well-being of the country with his own personal advancement," he said in a statement.
Former trade minister Craig Emerson said he was good friends through thick and thin with Mr Crean.
"A loyal servant of the Labor Party," Mr Emerson wrote on Twitter.
Former defence minister Joel Fitzgibbon tweeted: "I'm shocked by the news of Simon Crean's death. Far too young. A good and talented guy, history will treat him kindly."
After serving as federal Labor leader from 2001 to 2003, across the floor from John Howard, Mr Rudd appointed him the trade portfolio after securing a Labor victory in 2007.
After leaving politics Mr Crean continued to work for Australia's interests, most notably as chairman of the European Australian Business Council, Mr Albanese said.
The prime minister said the hearts of the Labor family went out to Mr Crean's beloved wife Carole, to his family and thousands of friends.
Local politicians also released tributes to the Labor stalwart.
"Vale Simon Crean, a wonderful Labor leader, Minister, legend and true believer," Wallsend MP Sonia Hornery said.
"A very sad loss for Australia. My thoughts go out to all of his family and loved ones."
Swansea MP Yasmin Catley described news of his death as "terribly sad".
"Vale Simon Crean. A proud advocate for working people and stalwart of the Labor movement," she said.
- With Australian Associated Press
