By Jim Muir BBC Tehran correspondent

Recent figures show that in little more than a decade, Iran has scored a stunning success in reducing its population growth rate, thanks to a vigorous state-supported family planning campaign.

It means that in the year 2006, the country's population is expected to be 37 million less than it would have been at the birth rates prevailing in the late 1980s, when the campaign began.

Couples can't get a marriage licence without attending contraception classes

Many taboos have been broken along the way.

The Keyhan Bod plant is about two hours drive to the west of Tehran, and is the only state-supported condom factory in the Middle East.

It produces about 45 million condoms a year, in 30 different shapes, colours and flavours.

"About 80% of our production is plain condoms destined for the Health Ministry," says general manager Kamran Hashemi. "The fancier ones go to the private sector. The favourite colour is pink, and for flavour, mint."

Changing times

If this seems anomalous in the Islamic Republic, Ahmad Shetabi, Keyhan Bod director, says times are changing.

"We may observe many restrictions because of our religion, but that doesn't mean we should reject this," he says.

"Probably we believe we have been behind, now we have to push ourselves forward. So why should we be hiding everything? Why shouldn't we be telling people that these condoms are good for you?

"Just as cigarettes damage your health, so condoms prevent damage to your body, disease or whatever else. So we are gradually accepting what is good for the people, and we follow that."

Most of the workers at the plant are women, wearing strict Islamic dress. If there was any embarrassment when they began work here, Zinat Rahmani, on the production line, says it's long since gone.

"Why should we feel embarrassed?" she asks. "The fact that we can stand on our own feet, and plan our own families and our society, is really good."

This openness means that anyone walking into an ordinary Iranian pharmacy may be greeted by a colourful display of condoms, many of them exotic foreign imports.

Free contraceptives

Contraceptive pills for women are also on sale. No questions are asked.

These and other contraceptive methods - along with advice - are also dispensed, free, at government primary health centres all around the country.

The state-supported condom factory produces 45 million condoms a year

Other methods are also available without payment.

The Shahid Jaafari no-scalpel vasectomy clinic in Tehran has so far performed nearly 30,000 operations on men who feel they have already had enough children.

It also trains doctors to carry out similar operations in other parts of the country.

"It's getting more popular now, being more accepted among the men," says Dr Ali Rasekhi, as he stitches one of his clients.

"Because the operation is now so unobtrusive, we give them the cut-out sections of vasectomy to prove to their wives that really they have had it done."

All this has fundamentally changed the way Iranians think about the family. In the past, big was the norm.

Now, as Dr Sidgh Azar, director of the vasectomy clinic says, people are opting for fewer kids and an improved quality of life.

"The culture of the people is changing, and they are going for a better life," he says. "To have a better culture and better education, people now believe they should have fewer children."

Birth rate stabilising

International population experts say this rapid transition from third-world to virtually European birth rate levels is almost unprecedented, and all the more remarkable because it has taken place in a conservative Islamic country which has now become an international success model.

To achieve this, the authorities had to reverse a trend set shortly after the 1979 Islamic Revolution. The gruelling 1980-88 war with Iraq prompted the Islamic government to encourage people to have more babies.

The birth rate soared. In the 10 years from 1976 to 1986, the population rose by 50%, from 33 million to 50 million.

Around 75% of sexually-active Iranians are now reckoned to be using modern contraceptive methods

At that rate, the census for the year 2006 would have registered 108 million Iranians.

But levels have been brought down so much that the current projection for 2006 is a much more manageable 71 million.

A strong measure of official encouragement has been crucial.

Obligatory contraception classes

Iran is believed to be the only country in the world where engaged couples cannot get a marriage licence unless they show that they have attended contraception classes.

In 1993, the state also dropped certain maternity benefits for those with more than three children.

Experts say that soaring literacy rates also helped spread the message that small families mean a better life.

Around 75% of sexually-active Iranians are now reckoned to be using modern contraceptive methods.

Mohammad Moslehuddin from Bangladesh, who heads the United Nations Population Fund office in Iran, is deeply impressed by Iran's success in stabilising its population growth.

"Even the developed countries took something like 35 to 40 years to reach these low birth rate levels, but Iran took just a little bit more than a decade," he says.

"That's obviously unusual, unprecedented and exemplary in the Islamic context.

"Other developing countries - in particular, the Muslim developing countries of the world - should learn from the successful experience of the Islamic Republic."