Iran's popular former president Mohammad Khatami has called for a nationwide referendum on the legitimacy of the government to end the country's post-election crisis. Mr. Khatami's proposal was reported by several reformist Web sites on Monday. Mr. Khatami also said Iranians have lost their faith in the ruling political system following the June 12 election. The opposition charges that President Mahmoud Ahmadinejad won the election through mass fraud. It is too early to say whether Mr. Khatami's call for a referendum would be adopted by authorities, but it constitutes the latest challenge to Ayatollah Ali Khamenei, Iran's supreme leader who has the last word on state matters. Khamenei has declared the results of the elections valid.