The human rights group says numerous former prisoners have implicated Said Mortazavi in torture, illegal detention, and the coercion of false confessions.
Mortazavi is also suspected of involvement in the killing of the Canadian-Iranian photojournalist Zahra Kazemi.
Canadian Foreign Minister Peter MacKay has said in a statement that Mortazavi's presence in Iran's delegation demonstrates Tehran's complete contempt for internationally recognized principles of human rights.
The Paris-based International Human Rights Federation has also condemned the move in an open letter to UN Secretary-General Kofi Annan, UN High Commissioner for Human Rights Louise Arbour, and officials on the UN's top body, the Security Council.
