Stephen Lewis, the Canadian diplomat, politician and human rights advocate, who spent decades tirelessly working to focus global attention on the HIV/Aids epidemic, has died of cancer.

Lewis, who served as the Canadian ambassador to the United Nations, as well as the head of Ontario’s New Democratic party (NDP), was 88.

“Stephen spent the last eight years of his life battling cancer with the same indomitable energy he brought to his lifelong work: the unending struggle for justice and dignity for every human life,” his family said in a statement. “The world has lost a voice of unmatched eloquence and integrity.”

Prime minister Mark Carney paid tribute to Lewis, calling him “a pillar of compassionate leadership in Canadian democracy, and a renowned global champion for human rights and multilateralism” in a statement.

Lewis, the scion of former federal NDP leader David Lewis, was also the father of Avi Lewis, who was elected leader of the federal NDP on Sunday.

In his victory speech before his father’s death, Avi Lewis paid tribute to him, saying his father was “not doing too well” but was hanging on from his hospital bed to see the next chapter of “the movement”.

“Ever the political fanatic, dad has demanded daily updates about our organizing, delivered to his hospital bed – a veritable IV drip of campaign data,” he said. “At age 88 he is more passionate about the promise of democratic socialism than he has ever been in his life.”

Stephen Lewis led the Ontario NDP from 1970 to 1978, serving as official opposition leader from 1975 to 1977.

After leaving politics, Lewis was appointed Canada’s ambassador to the United Nations. He was then named special adviser to the UN’s secretary general on African affairs and later became deputy director of Unicef and the United Nations special envoy for HIV-Aids in Africa.

It was that work, in a region of the world decimated by illness and the neglect of nations with the means to help, that left him shaken.

“I cannot remember in my entire adult life scenes of such unendurable human desolation, it was heartbreaking,” Lewis said during his first speech to the UN in 2006.

A skilled orator and writer, he reserved his sharpest criticism for wealthy nations and the global institutions capable of ending much of the suffering.

“It’s not just the fact that people will die; it’s the fact that those who have made the decision know that people will die. How does that get rationalized?” he said in a 2011 speech at Yale University after donor nations cut funding. “How does that get dealt with in the inner sanctums of development ministries and cabinet discussions? What in God’s name do they say to each other?”

Lewis, driven by the desire to make combating disease and poverty his life’s work, then co-founded the Stephen Lewis Foundation with his daughter Ilana Landsberg-Lewis, travelling often to countries in Africa disproportionately affected by pandemics.

During the coronavirus pandemic, Lewis called on nations like Canada to recognize the need for vaccine equity, and criticised the government for accessing doses from an international vaccine-sharing pool. “It was always understood from the outset that this was not a source of vaccines for the rich and wealthy countries of the world,” he said in a 2021 interview.

There are two schools in Toronto named after him and Lewis holds 33 honorary degrees, among the highest of any Canadian. He was given the Order of Canada, the country’s highest honour, in 2002.