Paul Vallely: Iran is dangerous. But attacked, it is more so

It has a nuclear programme and a repressive regime, but to square up to these with military action would destabilise the world

In ancient Persia, which is now Iran, there lived at the beginning of the third century a prophet by the name of Mani. He developed an exhaustive cosmology which saw the world as caught up in a struggle between a good spiritual realm of light, and an evil material force of darkness. It's a world view whose influence has never quite been vanquished, as our former prime minister Tony Blair demonstrates. His Manichean instincts were to the fore again last week when he said in the BBC interview to plug his new book: "I think it is wholly unacceptable for Iran to have nuclear weapons capability. I think we've got to be prepared to confront them, if necessary, militarily".

I had never expected Blair to apologise for the war in Iraq. Even if he wanted to, he could not; those who were against it would not be appeased and those whose soldier sons had died for their country might well feel betrayed if he were publicly to concede that their sacrifice had been demanded in error. But I had thought that, in his heart, he might know that it had all been a ghastly misjudgement. Not so, for the messianic glint was once again in his eye.

No one should have any illusions that Iran today is a very nasty place. Carla Bruni, the wife of President Sarkozy of France, discovered that last week when a state-run newspaper in Tehran labelled her a prostitute who should be stoned to death. Her offence had been to criticise the Iranian regime for sentencing a woman to death for adultery.

The sentence on the woman concerned, Sakineh Ashtiani, is under review after an international outcry. (She may now be hanged rather than stoned). But two other people received the same sentence for alleged adultery in Iran last week, so international opinion clearly has not had that much influence. Article 102 of the Iranian penal code states that men must be buried up to their waists, and women up to their necks, for the purpose of execution by stoning. This is to prevent stones from hitting a woman's breasts, to protect her modesty. And since stoning can end if the victim can struggle free, men have a considerably greater chance of escaping than do women.

But it is not only a barbaric judicial system that makes Tehran so unpleasant. Its democracy is a sham, as the rigged presidential elections last year showed, along with the violence against the supporters of the defeated candidate. Thousands of protesters were detained; 80 have been jailed and 10 sentenced to death.

Just last week, pro-government militia attacked the home of an opposition leader with home-made bombs while the police looked on. On Friday, the annual state-sponsored anti-Israel rally known as Quds Day was marked by the militia releasing at low prices to teenagers two new anti-Zionist video games – Satan's Den 2 and Attack on Freedom Flotilla.

But should the response be to bomb Tehran? There is a weary familiarity about the scenario. We saw it in Afghanistan and then Iraq and Iran seems next. First the place is denounced as a strategic threat. Next a casus belli is found: Afghanistan was hiding Osama bin Laden; Saddam supposedly had weapons of mass destruction; Iran is suspected of developing a nuclear bomb. Then come sanctions; we are currently in the fourth round against Tehran. And finally, inexorably, comes the "last resort": military action.

Iran has a developing programme to acquire nuclear power. Last Saturday, with UN-approved help from the Russians, it began fuelling its first nuclear power plant near Bushehr. It denies it has aspirations for a nuclear bomb, but you can see why they might want one. To the north, Russia has the bomb. To the east, Pakistan and India have too. To the west, Israel has an estimated 400 nuclear warheads – no one knows the exact number since Israel refuses to sign the nuclear non-proliferation treaty and allow inspections.

To fuel its nuclear power stations Iran is enriching uranium. But enriched uranium can also be used to make the fissile core of an atom bomb.

It would undoubtedly be better if Tehran did not have nuclear weapons. It could destabilise the region in a number of ways. It could spur an arms race across the region with Saudi Arabia, the Gulf states, Egypt and Turkey all rushing to acquire atom bombs. It might frighten the educated Israeli middle class into emigrating. Almost certainly it would allow Tehran to more forcefully back radical Islamist movements like Hizbollah and Hamas.

All that would be undesirable. But is it worth going to war over?

The elaborate game of bluff and double-bluff currently being conducted suggests not. President Ahmadinejad of Iran is a man of mixed signals. He was quoted in a Japanese newspaper on Friday as saying that Iran would stop higher-grade enrichment if it were guaranteed nuclear fuel supplies from outside. But the same day he told the Quds rally in Tehran that Israel and its supporters were too weak to attack Iran's nuclear facilities.

There is a lot of bluster about. Last month, Iran launched a new surface-to-surface missile which military observers assume must match or excel its existing missiles that have the range to hit Israel. But most strategic experts – even in Israel where the Prime Minister Benjamin Netanyahu once suggested that Tehran is "preparing another Holocaust for the Jewish state" – believe it is a weapon of retaliation rather than attack. Deterrence is the name of the game.

There are other grounds for caution. Were the Iranians to begin to produce material for a bomb – reconfiguring their nuclear facilities to produce weapons-usable plutonium – it would be swiftly obvious to the International Atomic Energy Agency. It would also know if Iran tried to divert spent nuclear fuel from Bushehr instead of returning it to Russia. The IAEA's former head, Mohamed ElBaradei, said last year that there was "no credible evidence" that Iran was developing a bomb and described the threat as "hyped".

Nor is there the common purpose in Tehran for a nuclear weapons programme. Intelligence suggests fragmented views among the leadership in the complex interlocking constitution which divides political control between the president, the Guardian Council, the Assembly of Experts, the head of the judiciary and the Supreme Leader Ayatollah Khamenei.

But the clincher is that all the war-gaming exercises done by the Pentagon show that an air assault on Iran's carefully dispersed and buried nuclear sites – which would inevitably kill civilians – would produce outcomes worse than living with an Iran with a nuclear weapon capability. The bombing would be a propaganda gift to anti-Western extremists. Terrorists from all over the world would report to Tehran for duty. Bombing could easily have the very effect it was designed to avoid – the rapid destabilisation of the entire Middle East.

This is not a situation which calls for leaders who see the world in black and white. Tony Blair, a religious man, would be well advised to remember who was the West's most famous Manichee. It was St Augustine who subsequently saw the light and became the scourge of the movement he had once embraced. Mani, and his followers, are all now officially heretics.