Senior Labour backbencher and Middlesbrough MP Sir Stuart Bell has died after a short battle with pancreatic cancer, his family has said.
The 74-year-old had been MP for the town for almost 30 years.
Labour leader Ed Miliband said: "The son of a North East miner, Stuart was fiercely proud to represent Middlesbrough."
Prime Minister David Cameron described him as "one of Parliament's great characters."
Sir Stuart first won his Middlesbrough seat in 1983 and went on to hold it through seven general elections.
Mr Miliband said: "Sir Stuart's death will come as a huge blow to his family and many friends and colleagues.
"He spent the long years of opposition fighting for the Labour Party to regain power and championed, throughout his life, the many causes that were close to his heart.
"He resigned from the opposition front bench to pursue his calls for justice for the children and families of the Cleveland child abuse scandal.
"He served the House of Commons and the Church of England as the Church Commissioner, a position he held for 13 years and was a passionate campaigner on European issues.
"Stuart was a dedicated family man and had a formidable partnership with his wife Margaret. All our thoughts are with her and his children."
Sir Stuart never served as a minister, but was the party's Northern Ireland spokesman in opposition during the 1980s.
After the 1992 general election he was made shadow trade minister under both John Smith and Tony Blair.
'Stood up for issues'
Later in his career he was handed a powerful role on the Commons Commission - the body responsible for running the House.
He played a central role during one of Parliament's most difficult periods as the long-running scandal of MPs' expenses abuses emerged in 2009.
And he provoked controversy in his own constituency when he stopped holding surgeries in 1997 after being assaulted.
In 2004 he was knighted for services to Parliament and awarded the Legion d'Honneur in 2006 for his contributions to Anglo-French relations. He was also a published novelist.
Mr Cameron said: "Throughout his three decades in the House of Commons, he always stood up for those issues he cared most deeply about.
"A firm advocate of church matters as Second Church Estates Commissioner for 13 years, and a member of the House of Commons Commission over a very challenging decade, he will be remembered for his kindness and his courtesy towards parliamentary colleagues."
Former Prime Minister Gordon Brown also paid tribute.
"Sir Stuart Bell combined great expertise with sound judgment," he said.
"He will be remembered for his commitment to Middlesbrough as a constituency MP and for his great enthusiasm for social justice, Europe and the best relations between Church and state, where his contribution will never be forgotten."
Middlesbrough South and East Cleveland Labour MP Tom Blenkinsop said: "I am extremely saddened to hear the news that my colleague and fellow Middlesbrough Labour MP has passed away after losing his fight with cancer.
"My thoughts and deepest sympathies are with his wife Margaret and all his family and friends."
Ian Swales, the Liberal Democrat MP for neighbouring Redcar, wrote on Twitter: "Very sad to hear of the death of Stuart Bell MP. Always a total gentleman to me."
Sir Stuart lived in Middlesbrough with his wife Margaret, with whom he had one son. He also had two children from a previous marriage.