Speaker Ali Larijani said the claims of rape and sexual abuse were unfounded
The speaker of Iran's parliament has dismissed claims by a defeated presidential candidate that opposition protesters were raped in detention.
"Based on parliament's investigations, detainees have not been raped or sexually abused in Iran's Kahrizak and Evin prisons," Ali Larijani said.
"Such claims are totally baseless," state television quoted him as saying.
Opposition leader Mehdi Karroubi called on Sunday for an inquiry into alleged rapes of male and female detainees.
In a letter to former President Akbar Hashemi Rafsanjani, now the head of a powerful adjudicating body, Mr Karroubi said some of the detainees had been seriously injured in the alleged sexual abuse.
Fellow opposition leader Mir Hossein Mousavi said the reports of abuse showed there was "a need for deep change" in Iran, according to his website.
On Wednesday another defeated presidential candidate, Mohsen Rezai, said that if the claims were proven then all the officials involved should be sacked and put on trial, and a day of national mourning declared.
The conditions under which detained protesters have been held has been controversial, with damaging claims forcing authorities to act.
The Supreme Leader, Ayatollah Ali Khamanei, closed the notorious Kahrizak detention centre saying it had failed to "preserve the detainees' rights".
Police officials have admitted that some of those held since June might have been tortured.
Both the Iranian parliament and judiciary have established committees to investigate the post-election unrest and the government's response.
BBC Tehran correspondent Jon Leyne says the issue of prison abuse is both a real concern in itself and also has become a way of criticising the government of President Ahmadinejad without directly challenging the legitimacy of his re-election.
On Tuesday, Iran's authorities said 4,000 people had been detained during the mass protests that broke out in the wake of the 12 June presidential poll, which the opposition says was rigged.
The number was much higher than previous figures, although the authorities said 3,700 of them had been released within a few days of arrest.
Opposition leaders say 69 protesters died in the post-election violence - more than double the official figure of about 30 fatalities.
Iran is currently trying more than 100 detainees over their alleged involvement in the protests.
The trials - of leading opposition figures, activists, journalists, lawyers, workers at foreign embassies and two people with foreign nationalities - have been criticised by several foreign powers, opposition groups and human rights campaigners.
But authorities insist their legal proceedings are completely legitimate and conform to international standards of justice.
Official election results awarded incumbent President Mahmoud Ahmadinejad a sweeping victory in the polls.
He is in the process of selecting a cabinet, which will be submitted to parliamentary approval next week.
Foreign media, including the BBC, have been restricted in their coverage of Iran in the wake of the election protests.