TEHRAN: A group of former reformist lawmakers appealed to a powerful religious body in Iran to investigate supreme leader Ayatollah Ali Khamenei’s qualification to rule in an unprecedented challenge to the country’s most powerful man over the postelection crackdown.

The call came as controversy heated up Friday over allegations that protesters detained during the crackdown were tortured. Hard-line preachers across the country demanded that a senior reform leader be prosecuted for claiming that some detainees were raped by their jailers.

The former lawmakers’ appeal was to the Assembly of Experts, a body of scholars that under Iranian law has the power to name the supreme leader and, in theory, to remove him — though such a move has never been attempted. There was no immediate response from the assembly to the group’s letter, sent late Thursday.

But even if the call is ignored and is only symbolic, it was the most direct challenge to Khamenei yet in the turmoil that has embroiled Iran since its disputed June 12 presidential election. The letter breaks a major taboo among Iran’s political classes against overtly targeting Khamenei, whose position at the top of the political-religious hierarchy has long been unquestioned. The letter came from a group of former lawmakers, most of them from the reform camp. The Web reports did not say how many signed the letter.

In it, they sharply denounce the crackdown, in which hundreds of protesters and opposition politicians were arrested and, the opposition says, 69 people were killed.

They also denounce the trial that began this month of 100 politicians and activists accused of seeking to topple the government through a wave of protests.

The former lawmakers said the supreme leader is responsible for the judicial system and the security forces who carried out the crackdown, adding that Iran’s constitution underlines that “the supreme leader is on the same level as the rest of the people before the law.” The former lawmakers “demand a legal probe on the basis of Article 111 of the Constitution, which is a responsibility of the Experts Assembly,” the letter said.

The letter was addressed to Ayatollah Ali Akbar Hashemi Rafsanjani, a powerful former president who heads of the Assembly of Experts. Rafsanjani has sided with the opposition in the election crisis.

In past weeks, there have been reports of young protesters who died while in prison, apparently from torture or other abuse. This week, Mehdi Karoubi, who lost to Mahmoud Ahmadinejad in the presidential election, went further, claiming that male and female detainees had been raped by their jailers. Parliament Speaker Ali Larijani quickly denied the allegations.

During his sermon at the Friday prayers in Tehran, Ayatollah Ahmad Khatami denounced Karoubi’s claims as “full of libel, a total slander against the Islamic system” and demanded he be prosecuted. In what appears to be a coordinated move, prayer leaders in Mashhad and Qom made similar calls in their sermons.