Authorities have charged Abbas Palizdar -- a supporter of President Mahmud Ahmadinejad -- with "spreading rumors" and "causing distress among the public."
The arrest comes just days after he publicly accused several prominent ayatollahs and leading members of parliament of pilfering state funds and obtaining favorable business arrangements for their relatives.
In an exclusive interview with Radio Farda on June 9, Palizdar claimed to have proof that top-level politicians -- including former President Ali Akbar Hashemi-Rafsanjani, who chairs the Assembly of Experts and the Expediency Council -- have been involved in illegal deals and criminal acts.
Palizdar also said he planned to reveal more information regarding corruption among the country's political elite.
"I spoke based on documents and evidence [in my possession]," he told Radio Farda. "There are many more cases that I will reveal in the future. Everything that I said -- if [the government] didn't add anything to it -- is based on proof and documents."
The accusations -- unprecedented for Iran -- came in late May in speeches that Palizdar gave at Bu Ali Sina University in the western Iranian city of Hamadan and at Shiraz University, in the southern part of the country.
Palizdar offered details of criminal offenses that he says were committed by several leading politicians and clerics who he claims accumulated hundreds of millions of dollars in illegal business deals.
Along with Hashemi-Rafsanjani, Palizdar singled out so-called traditional clerics, including the interim Friday Prayer leader of Tehran, Mohammad Emami Kashani; and the head of the Imam Reza Shrine Foundation, Ayatollah Vaez Tabbasi.
Iranian bloggers published portions of Palizdar's speech and exchanged views on what was an exceptional event for Iran. After the controversial speech, the Bu Ali Sina University's Islamic Society of Students was reportedly shut down.
Some observers say the accusations by Palizdar were an attempt to weaken some the president's rivals ahead of next year's presidential election.
A conservative faction hostile to Ahmadinejad and led by presidential rival and parliament speaker Ali Larijani, has dominated the Iranian parliament, the Majlis.
Others suggest that Palizdar -- who like many other pro-Ahmadinejad candidates was defeated in the last elections to Tehran's City Council -- is trying to gain revenge by making these accusations against his rivals.
Palizdar told Radio Farda that his accusations have "nothing to do with elections."
"I feel they try to give the impression that I'm saying these things because of the elections, but it has nothing to do with elections," Palizdar said. "I had some obligation on behalf of martyrs. It was my religious duty to bring up these things because I had a feeling that the Majlis has no intention to go forward on these issues. So, I did it myself."
Palizdar told Radio Farda that the Majlis had studied his report and sent it to the judiciary to be investigated.
The Majlis has reacted publicly to the claim by saying that Palizdar did not work for the parliament's research center and therefore had not been able to obtain any information regarding corruption.