MOSCOW, July 20 (RIA Novosti) - A former Iranian president and prominent leader of the country's reformist movement has called for a referendum as a means of overcoming the current political crisis in Iran, Al-Jazeera reported on Monday.

Mohammad Khatami said that "public confidence in the system has been damaged" by the alleged vote rigging and subsequent riots that followed the landslide reelection of hardline President Mahmoud Ahmadinejad on June 12.

Khatami served two presidential terms in 1997-2005, which were widely seen as a thaw in relations with the West. He currently heads a group of reformist clerics, the Association of Combatant Clerics.

"As millions of Iranians have lost confidence in the electoral process, the Association of Combatant Clerics insist on the organization of a referendum ... by independent bodies," Al-Jazeera quoted the group as saying in a statement.

Under the Iranian constitution only the country's supreme spiritual leader, Ayatollah Ali Khamenei, can announce a nationwide referendum. Khamenei, however, has upheld the election result and accused outside forces of stirring the unrest.

Last Friday a powerful Muslim cleric Akbar Hashemi Rafsanjani, also a former president, delivered a sermon casting doubt on the disputed election. He also said that voters' faith in the system must be restored. The sermon triggered a new wave of protests from supporters of the defeated presidential candidate Mir Hossein Mousavi.