A recent UN report on the human rights situation in Iran "lacks credibility and legality", Iran's foreign ministry spokeswoman Marzieh Afhkam said Thursday.
The report, by UN Secretary-General Ban Ki-moon, was "unacceptable and politically-motivated", Xinhua cited semi-official ISNA news agency as quoting Marzieh.
"The report lacks credibility and legality because of undocumented and non-legal charges" against Iran, she added.
"Parts of the released report indicate that the UN chief has not been impartial, hence tampered," she was quoted as saying.
On Wednesday, Ban criticised Iranian President Hassan Rouhani for not doing enough to improve the human rights situation in Iran since he took office last August.
Increased death sentences, arbitrary detention, unfair trials, discrimination against minorities and women, mistreatment of political prisoners and restrictions on freedom of speech are examples of rights violation by the Islamic republic, Ban said in his report.
He also called for "immediate release" of two reformist opposition leaders, Mir-Hossein Mousavi and Mehdi Karoubi, demanding their "urgent access to medical care".
Mousavi and Karoubi have been under house arrest after the 2009 presidential elections for leading massive rallies protesting what they called "fraud" in favour of hardline candidate Mahmoud Ahmadinejad.
Several Iranian hardline lawmakers and the judiciary have reacted angrily to Ban's report, saying that the report is an interference in Iran's internal affairs.
The Islamic republic has repeatedly dismissed reports by UN human rights institutions, saying that they do not reflect the realities on the ground in the country.