Nobel laureate JM Coetzee has declined to attend an upcoming literature festival in Israel, writing a excoriating letter to organisers citing the country’s “genocidal campaign” in Gaza, stating: “It will take many years for Israel to clear its name”.

The 86-year-old author, who was born in apartheid South Africa and lives in Australia, wrote to organisers of the Jerusalem international writers festival in November.

While the contents of Coetzee’s letter were described by the festival’s artistic director, Julia Fermentto-Tzaisler, to Israeli press in April, the Guardian has received Coetzee’s correspondence directly.

In reply to Fermentto-Tzaisler’s invitation to Jerusalem international writers festival, which takes place 25 to 28 May, Coetzee declined but added, “I wish to state the grounds on which I do so.”

“For the past two years the state of Israel has been conducting a genocidal campaign in Gaza that has been vastly disproportionate to the murderous provocation of 7 October 2023,” he wrote. “This campaign, conducted by the IDF, appears to have had the enthusiastic support of the vast majority of Israel’s population. For this reason it is not possible for any considerable sector of Israeli society, including its intellectual and arts community, to claim that it should not share in the blame for the atrocities in Gaza.”

Coetzee revealed he had once been a supporter of Israel, writing: “Until recently Israel enjoyed a broad measure of support in the West. I would number myself among such supporters: I kept telling myself that surely the day was coming when the Israeli people would have a change of heart and deliver some form of justice to the Palestinian people whose land they had taken over. It was in this spirit that I visited Jerusalem in 1987 to receive the Jerusalem prize.”

“The campaign of annihilation in Gaza has changed all that,” he continued. “Long-time supporters of Israel have turned away in revulsion at the actions of the Israeli military. It will take many years for Israel to clear its name, assuming that it wishes to do so, and to re-establish itself in the international community.”

Coetzee, who rarely gives interviews or makes public appearances, is arguably the world’s most decorated living author. He has won the Booker prize twice and was awarded the Nobel prize in literature in 2003.

When Coetzee went to Israel in 1987 to accept the Jerusalem prize – awarded to authors for their exploration of individual freedom in society – he used his speech to call for an end to apartheid in South Africa, saying: “South African literature is a literature in bondage. It is a less than fully human literature. It is exactly the kind of literature you would expect people to write from prison.”

The Guardian contacted Fermentto-Tzaisler, who did not reply by time of publication. She first revealed Coetzee had declined due to his views on Israel in April, telling Israeli news outlet Ynet that Coetzee sent a “especially harsh response” to her invitation and that it had “shocked” her.

In a reply letter quoted by Ynet, Fermentto-Tzaisler wrote to Coetzee, “As a South African writer who fought apartheid, I would have expected — or perhaps dreamed — that you would extend a hand to me, that you would say to me, ‘Fight, my daughter. Do not stop fighting.’ … You left me in despair.”

A UN special committee of inquiry found that Israel’s actions in Gaza, with mass civilian casualties and life-threatening conditions as well as statements by senior Israeli leaders, demonstrated “direct evidence of genocidal intent”. Amnesty International has said Israel is still committing genocide in Gaza during the ceasefire by continuing to target Gaza’s now mostly destroyed civilian infrastructure and restrict access to medical supplies and humanitarian relief.

Jerusalem international writers festival has hosted the likes of Margaret Atwood, Salman Rushdie, Jonathan Franzen, Joyce Carol Oates and Karl Ove Knausgård.