Iranian President Hassan Rowhani has failed to fulfil campaign promises to allow greater freedom of expression and there has been a sharp rise in executions since his election, UN Secretary General Ban Ki-moon said.
Rowhani, who won clearly in June, led Iran to a nuclear deal with world powers. But, perhaps wary of further antagonising hardliners, he has not made significant reforms that moderate voters had hoped for.
In a report to the UN Human Rights Council on Tuesday, Ban highlighted the prevalent use of capital punishment in Iran and called for the release of activists, lawyers and journalists as well as political prisoners that he said were in custody for exercising their rights to free speech and assembly.
"The new administration has not made any significant improvement in the promotion and protection of freedom of expression and opinion, despite pledges made by the president during his campaign and after his swearing in," Ban said.
"Both offline and online [news] outlets continue to face restrictions, including closure," he said.
Iranians expressing dissenting views or beliefs still faced arrest and prosecution, he added.
Ban welcomed the release of 80 political prisoners since September . But he said there still was a "large number of political prisoners", including lawyers, women rights activists and journalists.
Between 500 and 625 people were executed last year, including 57 in public, he said, echoing concerns by UN High Commissioner for Human Rights Navi Pillay.
More than 40 people were executed during the first half of January, Ban said.
"The new government has not changed its approach regarding the application of the death penalty and seems to have followed the practice of previous administrations, which relied heavily on the death penalty to combat crime," the UN leader said.