Sinn Fein president Gerry Adams has described Tony Benn as a true friend of the Irish people following his support for a united Ireland.
His republicanism and dealings with Sinn Fein long before IRA and loyalist ceasefires which ended the Northern Ireland conflict in 1994 provoked controversy, particularly his invitation to Mr Adams to come to Westminster.
The former West Belfast MP said: "Tony was a true friend of the Irish people.
"A principled politician and activist, he spoke up passionately for the idea of a united Ireland. He remained an avid supporter of Irish freedom throughout his life."
Mr Benn met the Sinn Fein leader on numerous occasions. He invited Mr Adams to a meeting in 1983 during the height of the IRA's campaign when the republican party's tolerance of violence was anathema to most in Great Britain.
After a visit by Mr Adams was blocked in 1993 he correctly predicted that he would eventually visit Downing Street, to become a regular occurrence during peace process negotiations under the Blair administration.
Many unionists profoundly disagreed with his stance.
East Antrim Democratic Unionist MP Sammy Wilson said: "He just followed the standard doctrinaire left wing view that republicans are good and unionists are bad. That permeated the left wing of the Labour Party."
Mr Benn, who died on Friday at the age of 88, once campaigned to have the Queen's head removed from stamps. He was a republican, advocating an end to the monarchy.
His interest in Northern Ireland was long-standing and helped keep the issue on the Westminster agenda.
Mr Adams, now a public representative in the Irish parliament, added: "Tony was a champion of the downtrodden and the voiceless in Britain, in Ireland and throughout the world.
"I met Tony many times over the years. He was a thoughtful and highly intelligent human being and a genuinely nice man, whom I will greatly miss."
In 2002, when the peace process was gridlocked over IRA arms decommissioning, the upper-middle class and nonconformist radical called for joint authority to be introduced by London and Dublin.
Ireland's foreign affairs minister, Eamon Gilmore, said he was a man of great integrity and determination.
"Tony was a most principled and respected parliamentarian and was also a great friend of Ireland.
"While his views on Northern Ireland were often seen as controversial, once the Good Friday Agreement was signed in 1998 he was among its strongest defenders."
Nationalist SDLP Foyle MP Mark Durkan said he was passionate in his politics, compassionate in his outlook and compelling in debate.
"For him politics was a battle of ideas, not a contest of image.
"He was always ready to argue issues on the basis of the interests at play and the rights at stake.
"Tony Benn was a great parliamentarian, wonderful platform orator and both personable and impressive in private conversation."]
Further readingTony Benn dead: Veteran Labour politician passes away aged 88