Iran's prosecutor general said Tuesday that opposition leaders Mir Hossein Mousavi and Mehdi Karroubi will remain under house arrest over anti-government protests until they "repent", Fars news agency reported.
Mousavi and Karroubi have been held incommunicado under separate house arrests since February 2011, accused of orchestrating massive, unprecedented street protests sparked by a disputed presidential election in 2009.
Prosecutor general Gholam Hossein Mohseni Ejeie said they had committed a "great crime and treason".
"Until time the sedition leaders (agree to) repent... the situation will remain as before," he said.
The protests turned deadly when authorities resorted to a heavy-handed crackdown in which thousands of protesters, reformist activists and journalists were arrested.
Mousavi and Karroubi had claimed that the 2009 election of Mahmoud Ahmadinejad as president for a second term had been rigged.
"Some people are pointlessly trying to lift the house arrests, but (their efforts) will not bear any fruit," said Mohseni Ejeie, without further details.
The fate of Mousavi and Karroubi -- both of whom are reportedly suffering health problems -- has attracted global attention and triggered heated debates at home.
In December influential Iranian lawmaker Ali Motahari, a conservative, said the judiciary should end the house arrests of Mousavi and Karroubi on put them on trial.
"The protracted house arrests without trial lack legal or religious justification," Motahari told parliament in remarks carried by the ISNA news agency.
Last week Karroubi was moved from a safe house to his own home, but still kept under house arrest, leading some to believe Iran was easing the terms of detention.
President Hassan Rouhani, a reputed moderate, pledged after his election victory in June 2013, to work for political and cultural liberalisation in Iran.
But he has stopped short of becoming directly involved in the case of Mousavi and Karroubi.
But in September, the authorities freed around 15 reformists, journalists and lawyers, notably prominent rights lawyer Nasrin Sotoudeh.