In a December 30 speech in the Iranian parliament, Motahari blasted the house arrest of opposition figures Mir Hossein Musavi and his wife, Zahra Rahnavard, and reformist cleric Mehdi Karrubi as illegal and anti-Islamic.
He also criticized the "harsh" sentences for those arrested in the 2009 crackdown that followed the disputed reelection of Mahmud Ahmadinejad and added that the former president should be put on trial along with Musavi and Karrubi, who challenged his reelection.
He said those arrested in the 2009 unrest should have an open trial. "As long as one side doesn't have the right to express itself and the other side says whatever it wants, this crisis will not be resolved," he said.
In his speech, Motahari pointed to an open secret: he suggested that Iran's powerful judiciary is not independent, a charge judiciary officials have repeatedly denied.
"Instead of chanting slogans about the sedition [the 2009 protests over Ahmadinejad's reelection], it would be better if the head of the judiciary would try to resolve it. The resolving of [the issue] requires an independent judiciary, not one that is influenced by this and that body and security and intelligence organs," he said.
The Tehran prosecutor's office said over the weekend of January 4-5 that it had launched a criminal case against the outspoken Motahari over his speech. In a statement issued by Iranian news agencies, prosecutor Jafar Dolatabadi said that Motahari's remarks on the need for an independent judiciary implies "insult" against judges.
The semi-official hard-line Fars news agency said that Motahari had been summoned to the Revolutionary Court for explanations. No date was announced.
Meanwhile, Iranian news agencies reported that Motahari's personal website was blocked inside the country.
Motahari responded by accusing the judiciary of an attempt to silence its critics. He said that according to the Iranian Constitution, it is his right as a member of parliament to comment on the country's affairs. He called the judiciary's action "illegal."
"If members of the parliament are prevented from speaking about such issues, they should close down the parliament," he said.
Motahari, the son of one of the founders of the Islamic republic, has also in the past criticized pressure on reformist figures and opposition members and called for the release of political prisoners. He has accused the powerful Islamic Revolutionary Guards Corps of having interfered in past parliamentary elections, and spoken against the arrest of journalists.
Last year Motahari said he had discovered surveillance equipment in his office.
Earlier this week, parliament speaker Ali Larijani, whose brother Sadeq is the head of the judiciary, said that although some of the claims made by Motahari were "untrue" and "humiliating," the filing of a criminal case against him by the prosecutor's office was unjustified.
In 2002 , then-lawmaker Hossein Loghmanian was put on trial and sentenced to prison for criticizing the judiciary. He was released after an outcry among his colleagues, including former parliament speaker Mehdi Karrubi, who threatened to resign.
-- Golnaz Esfandiari