Iranian supreme leader Ayatollah Ali Khamenei on Monday warned reformists not to disturb the country's security, in a strong threat to the opposition to back down after one of its top figures called for a referendum on the government. Khamenei addressed "Iran's elite" and warned them to be cautious in the positions they take on the turmoil that has shaken the country since the disputed presidential election on June 12. He said that hurting Iran's security was "the biggest vice," adding that "anybody who drives the society toward insecurity and disorder is a hated person in the view of the Iranian nation, whoever he is." Khamenei did not mention any names, but the comments reported on state radio were clearly directed at Mir Hossein Mousavi, the pro-reform candidate who claims to have won the election, and Akbar Hashemi Rafsanjani, the powerful cleric who on Friday criticized the leadership over the elections in a clear challenge to Khamenei. Khamenei, who holds final say in all state matters in Iran, has declared valid the re-election of President Mahmoud Ahmadinejad and has demanded a stop to questioning the results. Mousavi and his camp claim Ahmadinejad's win was fraudulent and that the new government he is to form next month will be illegitimate. Security forces crushed pro-Mousavi protests by hundreds of thousands of people in the weeks after the elections. But despite the suppression and demands by hard-line clerics that they obey the supreme leader, the opposition has continued pushing its campaign against Ahmadinejad. In Rafsanjani, the opposition has gained a powerful proponent within the clerical leadership that stands more powerful than the elected government. Emboldened by Rafsanjani's support for the opposition in a Friday prayer sermon last week, a leading reformist, former President Mohammad Khatami, called for a referendum to rule whether Ahmadinejad's government is legitimate and for a neutral body to oversee the vote. "The durability of order and continuation of the country's progress hinge on restoring public trust," Khatami said Sunday according to reformist Web sites. "I openly say now that the solution to get out of the current crisis is holding a referendum." The Association of Combatant Clerics, a reform-minded clerical group to which Khatami belongs, echoed his call, saying in a statement that a referendum is needed because "millions of people have lost confidence in the electoral process." Under Iran's constitution, a referendum has to be ordered by Khamenei himself. All popular votes in Iran are monitored by a powerful body of clerics called the Guardian Council. That council, which is dominated by hard-liners, oversaw the June 12 vote, then held a partial recount on orders of Khamenei to clear up the controversy. It ruled the results clean, but the opposition dismissing the recount, accusing the council of openly backing Ahmadinejad. Khatami and the clerical group, however, proposed that "a neutral body" should monitor the proposed referendum instead. They proposed the Expediency Council, another clerical body that is headed by Rafsanjani. "Of course, the referendum needs to be monitored not by bodies that brought this fate to the election but by a neutral body that people can trust," the association said, in a jab at the Guardian Council. Khatami accused hard-liners of undermining democracy and challenging the foundations of the Islamic Republic, which in theory is supposed to meld a democratic system with a theocracy carried out by clerical rule. "Not only the republicanism but also the Islamism of the system has been harmed. We need to ask the people whether they are satisfied with the current situation? If a majority of the people are happy with this situation, we will submit [to their vote]," he said. In his sermon Friday, Rafsanjani, also a former president, cast doubt on Ahmadinejad's victory and reprimanded the clerical leadership for its harsh crackdown against peaceful protests and for not listening to the claims of fraud. Rafsanjani called for the release of all those detained. He also accused hard-liners of undermining the republicanism of the system and ignoring people's vote. In related news, Iran on Sunday released on bail an Iranian employee of the British Embassy who it had charged with harming national security by his alleged involvement in the protests, said the man's lawyer, Abdolsamad Khorramshi. Hossein Rassam, the embassy's chief political analyst who was jailed June 27, was released from Evin prison in Teheran on bail of about $100,000, said Khorramshi. His court date had not yet been set, he said. Iran arrested nine local employees of the British Embassy in June, saying they were involved in the protests. The others were released, and Rassam is the only one who has been charged. British Foreign Secretary David Miliband welcomed Rassam's release and criticized the Iranian government for arresting the embassy employees. "The detention of embassy staff was completely unjustified: I am confident that none of them were involved in any improper behavior," said Miliband in a statement.