The Iranian Supreme Leader, assailed by some of his country’s most prominent clerics and detested by millions of his ordinary citizens, has received a boost from an unlikely quarter: Joe Biden.

One day after the American Vice-President said that the US would not stop Israel bombing Iran’s nuclear plants , Ayatollah Khamenei launched a fierce attack on “meddling” Western leaders, designed to rally his fractured people.

“We warn the leaders of those countries trying to take advantage of the situation: beware. The Iranian nation will react,” the Ayatollah declared in a televised speech yesterday. “The leaders of arrogant countries, the nosey meddlers in the affairs of the Islamic Republic, must know that even if the Iranian people have their differences, when your enemies get involved, the people . . . will become a firm fist against you.”

Tehran has backed the warning with action against foreign interests in Iran: a local employee at the British Embassy, Hossein Rossam, has been arrested and faces charges of threatening Iranian national security. An unnamed 23-year-old French woman working as a teaching assistant at the university of Isfahan was held last week on spying charges.

Bernard Kouchner, the French Foreign Minister, called the charges absurd, telling France Info radio station yesterday: “She took part in demonstrations which, as you know, attracted hundreds of thousands of Iranians and . . . she took photographs in all innocence. That’s what she’s accused of.”

Ayatollah Khamenei said that interventionist comments by outside countries would have a “negative impact” on future relations with Iran; a not-so-veiled threat at a time when the West is anxious to resume negotiations to halt the Islamic Republic’s nuclear programme.

In recent days several powerful clerics have openly challenged the Supreme Leader by refusing to accept the re-election of Mahmoud Ahmadinejad.

On Saturday the influential Association of Researchers and Teachers of Qom challenged the “victory” over Mir Hossein Mousavi. Yesterday the association’s leader, Grand Ayatollah Hossein Mousavi Tabrizi, urged Mr Mousavi to form a political party to fight for justice. Analysts expect more clerics to speak out.

Many hardline clerics still back Ayatollah Khamenei and Mr Ahmadinejad, and control key bodies such as the Guardian Council — but the dissident clerics do matter. Many were close to the late Ayatollah Khomeini, father of the Islamic Republic, and have impeccable revolutionary credentials. They can mobilise hundreds of thousands of followers.

“This is the first time so many clerics have refused to accept the leader’s word,” one Iranian analyst said. “His legitimacy has been destroyed, and he either has to rule by force alone or lose face and back down.”

Ayatollah Khamenei, 69, was President from 1981 to 1989, and was the compromise candidate to succeed Khomeini when the Supreme Leader died in 1989. He has increasingly allied himself with hardliners and backed Mr Ahmadinejad in the presidential election of 2005 in the hope that he could be easily controlled.

“The Supreme Leader is supposed to remain above the political fray, but Mr Khamenei has shown himself to be partisan — at considerable cost to his office and himself,” the analyst said.

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