A bill calling on Iran to join an international agreement on women's rights has been rejected by the government's supervisory body.
The Guardian Council has defied parliament and rejected an international treaty which aims to eliminate discrimination against women.
Iranian state television said the Council had decided to turn down the United Nations' convention claiming it was against Sharia law and the constitution.
Iranian women are treated like second class citizens
The reformist-dominated parliament ratified the bill last month believing it would help promote Iran's image abroad and help domestic problems at home.
That decision provoked bitter denunciation by hardliners, many of whom claimed the convention was colonialist and against the Islamic code.
The decision to reject the UN convention aimed at improving women's rights will come as no surprise.
The unelected Guardian Council, which vets all legislation in accordance with Sharia law, is controlled by hardliners.
They have rejected scores of bills passed by parliament, including several on human rights.
The issue of signing up to the convention has created much debate in Iran.
Earlier this month, dozens of clerics held street demonstrations in the holy city of Gom to protest against parliament's decision.
Although expected, this rejection is likely to disappoint the 13 female members of parliament.
They were hoping the convention would pave the way for achieving greater equality between men and women.
In their defence, they also noted that 168 countries, including several Islamic states, have signed the convention.
Despite enjoying greater freedoms than many other Islamic countries, Iranian women are treated as second class citizens.
In the courts they are worth half the value of men, have fewer rights in divorce and child custody and need their husband's permission to work or travel abroad.