"We unfortunately do not consider Ahmed Shaheed to be an impartial rapporteur," foreign ministry spokesman Abbas Araqchi said during his weekly briefing with reporters in Tehran, Iranian media reported.
Araqchi said Tehran had received two official letters from Shaheed requesting access to assess the human rights situation in the country.
But such a visit, he said, would not happen as long as Shaheed "continues his trend of writing unfair reports about Iran."
Shaheed has thus far relied on contacting campaigners and victims inside Iran, as well as exiles and human rights groups, to write his reports on the country.
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In March, the UN body monitoring human rights in Iran sounded the alarm after Shaheed's latest report touched on restriction of freedom of speech and a slew of other abuses, including torture, forced confessions, secret executions and the jailing of members of the political opposition.
Iran has accused Shaheed of failing to consider whether the international community was breaching the rights of its people by imposing sanctions over Tehran's controversial nuclear drive.