Tributes have been paid to Ivan Cooper, a founder of Northern Ireland’s civil rights movement, who has died aged 75.

The former politician, one of the few Protestant leaders who marched with Catholics on Bloody Sunday, died in hospital on Wednesday.

Born into a working-class family in Killaloo, near Derry, he was a founding member of the nationalist Social Democratic and Labour party in 1970 and served as an MP at Westminster and as a community relations minister during the Sunningdale administration in 1974.

Colum Eastwood, the SDLP leader, said Cooper embodied Ireland’s contrasting traditions and campaigned for fairness for people regardless of their background.

“Ivan Cooper was born to break the mould. A working-class Protestant man who saw a common injustice and inequality that had taken root in Protestant and Catholic communities, he dedicated his life to fighting it,” he said.

“Organising marches in Derry for the right to a home, the right to a job and the right to a vote, Ivan often put himself in the path of danger to secure justice for people in every community. And on many occasions that meant that he suffered vilification and violence for his convictions. It never stopped him.”

Eastwood said that along with John Hume, a former SDLP leader, Cooper helped “blaze the trail” that led to the 1998 Good Friday agreement.

Cooper wanted Catholics and Protestants to form a united front against injustice, but the violence and polarisation of the Troubles swept aside that vision. Many Protestants considered him a traitor.

He was with civil rights marchers on 30 January 1972 when British soldiers opened fire, killing 14 people. He once told the BBC he “always regretted” organising the march because no political cause was worth a life.

The actor James Nesbitt, who played Cooper in the film Bloody Sunday, said he was brave, brilliant and humane. “He was a sparkly man, a teller of tall stories, remarkably funny and extremely charming - but his impact on the peace process should never be underestimated.”

Cooper quit politics in the 1980s. The Irish president, Michael D Higgins, gave him a civil rights award last year.

Cooper, right, with John Hume in 1970. Photograph: Leif Skoogfors/Getty Images

Robin Swann, the leader of the Ulster Unionist party, said Cooper’s commitment to non-violent, peaceful and democratic methods was an example for Northern Ireland. “Had voices like his prevailed, we could perhaps have been spared the disaster and misery that was the Troubles,” he said.

Pat Hume said Cooper walked hand-in-hand with her husband, John, in seeking a non-violent, non-sectarian Northern Ireland.

“His commitment and courage and his desire and determination to tackle these issues never waned … Ivan Cooper will for ever hold a special place, not only in our hearts, but in the history of this island and in the continuing of the fight for civil rights and social justice.”