"We ask the UN: How can you elevate a regime that beats, blinds, tortures and rapes women who demand their rights?" the group wrote. "Where is the logic? Where is the morality?"

"It's time for all democracies at the UN to stop legitimizing murderous regimes, in violation of the world body's founding principles, and instead to begin holding the perpetrators to account," he said.

"The murderous regime in Tehran is responsible for a surge in executions, disproportionately applied to minorities, and for oppressing women and girls. The recent death of 16-year-old Armita Geravand, after being assaulted on the subway by the Iranian morality police for not wearing the compulsory hijab, is a reminder that this is a cruel regime that does not belong on any UN human rights body, let alone as chair."

He said it was "unimaginable" that Ayatollah Khamenei's representative would be charing the forum, standing alongside other dignitaries.