Former cabinet minister and veteran left-wing campaigner Tony Benn has died at home, his family has said.
The 88-year-old former Labour MP had been seriously ill.
Mr Benn became an MP in November 1950 and served in the cabinet under Harold Wilson and James Callaghan.
A major figure on the left of the party, he narrowly missed out on the deputy leadership in 1981 and went on to be a popular public speaker, anti-war campaigner and political diarist.
In a statement his children Stephen, Hilary, Melissa and Joshua said Mr Benn died peacefully early this morning at his home in west London surrounded by his family.
"We would like to express our heartfelt thanks to all the NHS staff and carers who have looked after him with such kindness in hospital and at home," the family said.
"We will miss above all his love which has sustained us throughout our lives. But we are comforted by the memory of his long, full and inspiring life and so proud of his devotion to helping others as he sought to change the world for the better."
They said arrangements for his funeral will be announced in due course.
'He treated me as an equal'
Aged just 25 when he first entered Parliament, Mr Benn subsequently had to find a way to renounce his peerage to remain in the House of Commons.
He served as an MP for more than 50 years, becoming secretary of state for industry in 1974 under Harold Wilson and going on to become secretary of state for energy, keeping his post after James Callaghan became PM.
But after the Labour government was ousted in 1979, he staged a bitterly divisive battle as the champion of the left with Denis Healey for the deputy leadership of the party.
He famously retired from Parliament in 2001, saying he wanted to "spend more time on politics" and became known as a prolific diarist.
The last of his nine volumes of diaries was published in October.
Labour leader Ed Miliband led the tributes to an "iconic figure of our age".
"He will be remembered as a champion of the powerless, a great parliamentarian and a conviction politician," Mr Miliband said.
"Tony Benn spoke his mind and spoke up for his values. Whether you agreed with him or disagreed with him, everyone knew where he stood and what he stood for."
Tributes to the veteran politician have been paid by Prime Minister David Cameron and Ed Miliband, leader of the Labour party
Mr Miliband revealed he paid a visit to Mr Benn in hospital recently, describing him as being "as sharp as ever in mind".
He said: "As I left he said to me 'Well, old son. Let's have a proper talk when you have more time'."
He added: "He believed in movements and mobilised people behind him for the causes he cared about, often unfashionable ones. In a world of politics that is often too small, he thought big about our country and our world.
1925 Born Anthony Neil Wedgwood Benn in London
1943 Serves in the Royal Air Force
1947 Elected President of the Oxford Union
1950 Wins by-election as Labour candidate for Bristol
South at 25
1960 Becomes peer on death of his father, which
prevents him sitting in House of Commons
1963 Becomes first Peer to renounce his title.
Re-elected in Bristol South-East by-election
1967 Promoted to front bench as Minister of
1981 Loses Labour Party deputy leadership election
to Denis Healey
1983 Benn's seat abolished by boundary changes.
1984 Wins by-election for Chesterfield
1988 Loses Labour Party leadership election against
2001 Does not stand in general election. Becomes
president of the Stop the War coalition
2008 Publishes latest version of his diaries
Source: BBC History
"Above all, as I had cause to know, he was an incredibly kind man. I did work experience with him at the age of 16. I may have been just a teenager but he treated me as an equal.
"It was the nature of the man and the principle of his politics."
'Never a dull moment'
He added: "All of my condolences go to his children Stephen, Hilary, Melissa and Joshua and his wider family. In their own ways, they are all a tribute to him as a father, a socialist, and a most decent human being."
Prime Minister David Cameron said: "I am sorry to hear that Tony Benn has died.
"He was a magnificent writer, speaker, diarist and campaigner, with a strong record of public and political service.
"There was never a dull moment listening to him, even when you disagreed with everything he said."
Former prime minister Gordon Brown also paid tribute to a "powerful, fearless, relentless advocate for social justice and people's rights".
He said Mr Benn's speeches will continue to have a "profound influence on generations to come".
'Clarity of expression'
Former foreign secretary Dame Margaret Beckett told BBC Radio 4's Today programme Mr Benn had been a brilliant speaker.
"People who heard him speak up and down the country will never forget it," she said.
"He had such clarity of expression, he opened people's eyes and he made them think."
Former cabinet minister Peter Hain said: "Tony Benn was a giant of socialism who encouraged me to join Labour in 1977: wonderful inspirational speaker and person: will be deeply missed."
Labour MP for Hackney North and Stoke Newington Diane Abbott also paid tribute to Mr Benn.
"Admired so many things about Benn: unwavering principles; always open to new ideas; stellar political speaker but unfailingly courteous," she said.