In a public review of Iran's record at the UN Human Rights Council, Britain, France, the United States and other Western nations expressed deep concern about reports of killings, arrests and torture in a clampdown on dissent.
"The authorities are waging bloody repression against their own people, who are peacefully claiming their rights," French ambassador Jean Baptiste Mattei said.
"France recommends that Iran accept the creation of a credible and independent international inquiry mechanism to shed light on these violations," he told the council.
The United States and Britain called on Iran to open up to visits by the United Nations investigator on torture as well as other human rights experts, who have failed to get into the country since 2005.
Despite Iran's stated commitments to uphold fundamental freedoms, "grave human rights violations continue to be committed," said British ambassador Peter Gooderham.
Michael Posner, US assistant secretary for democracy and human rights, said Washington "strongly condemns the recent violent and unjust suppression of innocent Iranian citizens."
They also urged a halt to executions of child offenders, "disporportionate use" of the death penalty against political opponents, violence against women, discrimination and a clampdown on free speech.
President Mahmoud Ahmadinejad's disputed re-election last June plunged the Islamic republic into one of its worst ever political crises, with the opposition refusing to take the fight off the streets despite often deadly crackdowns on protests.
Backed by Cuba, Syria and Venezuela, Mohammad Larijani, secretary general of Iran's High Council for Human Rights, defended Tehran's legal safeguards and accused foreign nations of supporting "terrorist" groups on its borders.
"With the victory of the Islamic revolution, the situation of human rights has consistently been used as a political tool to apply pressure against us and to advance certain ulterior political motives by some specific Western countries," Larijani told the UN Council.
Iranian officials also highlighted steps to improve women's access to education, health and social status, and to protect children as well as the representation of religious minorities, and to combat traditions such as forced marriages.
"The Iranian society is a successful model of brotherly and amicable coexistence," Larijani noted.
Russia along with some non aligned and Islamic nations noted social and economic development in Iran and called on Tehran to "continue to improve" human rights.
All UN member states must submit to a four-yearly review by the 47 countries in the Human Rights Council, which can only compile recommendations.
US Secretary of State Hillary Clinton said on Monday that she feared Iran was moving towards a military dictatorship, with enterprises controlled by the Revolutionary Guard "supplanting" the government.
