A senior Iranian cleric says women who wear revealing clothing and behave promiscuously are to blame for earthquakes.

An Iranian woman waits for the bus under a poster of Mahmoud Ahmadinejad Photograph: Behrouz Mehri/AFP/Getty Images

Iran is one of the world's most earthquake-prone countries, and the cleric's unusual explanation for why the earth shakes follows a prediction by the president, Mahmoud Ahmadinejad, that a quake is certain to hit Tehran and that many of its 12 million inhabitants should relocate.

"Many women who do not dress modestly ... lead young men astray, corrupt their chastity and spread adultery in society, which increases earthquakes," Hojatoleslam Kazem Sedighi was quoted as saying by Iranian media. Women in the Islamic Republic are required by law to cover from head to toe, but many, especially the young, ignore some of the more strict codes and wear tight coats and scarves pulled back that show much of the hair. "What can we do to avoid being buried under the rubble?" Sedighi asked during a prayer sermon last week. "There is no other solution but to take refuge in religion and to adapt our lives to Islam's moral codes." Seismologists have warned for at least two decades that it is likely the sprawling capital will be struck by a catastrophic quake in the near future. Some experts have even suggested Iran should move its capital to a less seismically active location. Tehran straddles scores of fault lines, including one more than 50 miles long, though it has not suffered a major quake since 1830.

In 2003, a powerful earthquake hit the southern city of Bam, killing 31,000 people – about a quarter of that city's population – and destroying its ancient mud-built citadel.

"A divine authority told me to tell the people to make a general repentance. Why? Because calamities threaten us," said Sedighi, Tehran's acting Friday prayer leader. Referring to the violence that followed last June's disputed presidential election, he said: "The political earthquake that occurred was a reaction to some of the actions [that took place]. And now, if a natural earthquake hits Tehran, no one will be able to confront such a calamity but God's power, only God's power ... So let's not disappoint God."

The Iranian government and its security forces have been locked in a bloody battle with a large opposition movement that accuses Ahmadinejad of winning last year's vote by fraud.

Ahmadinejad made his quake prediction two weeks ago but said he could not give an exact date. He acknowledged that he could not order all of Tehran's 12m people to evacuate. "But provisions have to be made ... at least 5 million should leave Tehran so it is less crowded," the president said.

The welfare minister, Sadeq Mahsooli, said prayers and pleas for forgiveness were the best "formulae to repel earthquakes. We cannot invent a system that prevents earthquakes, but God has created this system and that is to avoid sins, to pray, to seek forgiveness, pay alms and self-sacrifice," Mahsooli said.