More than a dozen prominent authors and literary figures have withdrawn from PEN America’s flagship World Voices Festival in protest of what they see as an inadequate response by the organization to the “genocide” being committed against Palestinians by Israel in Gaza.

The group of writers, which includes Naomi Klein, Michelle Alexander, Hisham Matar, Isabella Hammad and Zaina Arafat, sent a letter to PEN America asserting it had “betrayed the organization’s professed commitment to peace and equality for all, and to freedom and security for writers everywhere” by failing to call for a ceasefire in the Israel-Gaza war.

The protest, first reported Thursday by Literary Hub, is the latest broadside directed at the literary freedom advocacy organization following a series of high-profile resignations and other denouncements in recent weeks.

In January, authors Angela Flournoy, a national book prize finalist, and Kathleen Alcott, winner of the O Henry prize, withdrew from a PEN new year event in Los Angeles to oppose the organization’s sponsorship of a separate gathering featuring Mayim Bialik, an author, actress and vocal supporter of Israel’s military action.

Last month, hundreds of writers including Roxane Gay, Maaza Mengiste and Nana Kwame Adjei-Brenyah wrote to PEN condemning what they called its “silence” over “Palestinian journalists, writers, and poets murdered by Israel” outside of “press releases buried on its website”.

Literary Hub says that open letter has now surpassed 1,300 signatories.

In the latest missive, the 16 authors say their decision to pull out of the festival, scheduled to take place in New York from 8-11 May, follows PEN’s “failure” to support human rights organizations and the United Nations security council in demanding a Gaza ceasefire.

“Palestine’s poets, scholars, novelists and journalists and essayists have risked everything, including their lives and the lives of their families, to share their words with the world,” the letter states.

“Yet PEN America appears unwilling to stand with them firmly against the powers that have oppressed and dispossessed them for the last 75 years. An unrelenting genocidal campaign is currently being waged against Palestinians in Gaza, a horror that has been filmed daily and streamed live around the world.

“We hope that our decision not to participate will add to existing efforts to yield concrete and lasting change at a time that calls for moral courage from us all.”

Klein, author of several award winning books about social and climate justice, expanded on her reasoning in a separate post on X, formerly Twitter. “5 months ago, PEN America asked me to be an honourary co-chair of this year’s World Voices Festival. I was honoured. Then I watched what PEN did – and failed to do – about Gaza.”

The letter, which is also signed by members of the Worker Writers School, concludes by acknowledging PEN America “can be open to criticism and has responded by adding new pages to its website and issuing new statements”, developments the authors say are “welcome but still not enough”.

In a statement supplied to the Guardian, Suzanne Trimel, PEN America’s senior adviser for communications and media, said the organization respected the writers’ decision.

“PEN America is devoted to free speech and the role of writers. We are anguished at the grave and intensifying crisis in Gaza and its effect on Palestinian civilians and the hostages. We stand with the poets, authors, scholars and writers whose lives and wellbeing have been devastated by this war,” the statement said.

“We are all aghast witnessing the brutal toll of human suffering. But beyond that, there are divergent views on questions of deep consequence. For some, referencing nuance is moral betrayal. For others, failure to do so is unconscionable. We face the challenge of applying our mission and principles in this moment, and hear from stakeholders who interpret them in sharply different ways.”

The statement continued: “When it comes to participation in the World Voices Festival, writing is an act of conscience, and we respect writers following their own. We invited these writers to participate in the Festival because we think their voices matter; we appreciate their speaking out and plan to respond.”