For citizens going into battle against Afghanistan's officialdom, the warren-like building across the road from the headquarters of Kabul's police chief is a one-stop shop for every document they could need.

From their tiny cubbyhole offices, an army of typists can run up everything from marriage certificates to CVs and job application letters. Also available, for several hundred dollars more: Taliban death threats, the special chits also known as "night letters" that can be a passport to a new life in the west.

"We can write whatever you need; it depends," said one young clerk. "For example, we will mention you work in a government department, your job title and salary. It will say, 'If you don't leave your job by this date, we will come and kill you or put a bomb in your house'.

"Or we can say you are working with US forces," he added.

For a large number of Afghans such a purchase is just the first of many expensive outlays on the high-risk road to a new life in the west. Buyers hope the document will persuade immigration officers many thousands of miles away to give them asylum in Europe or Australia. The document is one part of a growing and lucrative business in smuggling a tide of mostly young, unaccompanied Afghan males overseas.

One people smuggler was happy to talk business after a perfunctory introduction in a car next to a police checkpoint in Kabul. He said two factors were driving a boom in his business: the rising fear among some Afghans for the future of their country and the existence of a class of well-off professionals who can afford his huge fees.

"Every day I am helping more people from all corners of Afghanistan to get out of the country," he said. "If everyone had money, then everyone would leave."

The Afghan government recently reported that around 50,000 Afghans cross illegally into Greece each year, a country which is both on the outer reaches of the Schengen zone and relatively easily reached from Turkey.

Smugglers offer different packages depending on what people can afford. By far the most expensive option, often in excess of $20,000 (£13,000), involves the elaborate forgery of European passports, or tinkering with legitimate ones, which allows his wealthiest clients to fly directly to their target country. "Eighty per cent of my customers go on a fake passport to Britain," confides a smuggler working in the eastern city of Jalalabad. "If you have money, everything is possible because we have contacts in western countries who make them for us."

A high proportion of his customers choose to fly from Islamabad and travel under fake Pakistani passports. "We have people at the airport who make sure they will get through customs," he said. "The deal we have is that once the customer is successfully on the plane, he has to pay. When they get to the UK they are on their own. We tell them to lose their documents when they arrive and go to the police at the airport."

He oversees the departure of around 15 people a month by plane. He also assists around 100 people each month who can only afford to travel by land, a figure that quadruples in the summer when the mountain paths between Iran and Turkey are less treacherous.

That was the route tried by Mohammad Nasim, a 21-year-old from a well-off family who decided to try and leave his country after his brother was killed by a bomb at the Indian embassy in Kabul.

His ultimate destination was the UK, but he only got as far as the Greek border after walking over the mountains from Iran into south-east Turkey. Around 40 other Afghans were in the group walking under cover of darkness along mountain tracks. With fake passports they then travelled by car to Istanbul, but the expensively acquired documents failed him when he tried to cross into Greece.

"I'd agreed to pay $18,000 if I got to England, but I only had to give them $5,000 in advance," said Nasim. "I was just unlucky when they checked my document on the computer."

He was deported back to Iran where he was kidnapped by a criminal gang before being allowed to return to Kabul after his family paid a ransom.

Becoming victims of such criminality and exploitation is a constant risk. The situation for marooned Afghans in Greece is so bad that the Afghan government plans to open an embassy in Athens to help deal with tens of thousands whose dreams of moving deeper into Europe have turned into a nightmare of limbo with no money or papers. Their plight is often made all the worse by smugglers who keep their passports until they are paid in full.

"It is a lot more difficult to get asylum protection in Greece so it is just a transit point," said Jean-Philippe Chauzy, a spokesman from the International Organisation of Migration. "There is a lot of resentment against migrants in Greece, especially with the economic crisis, which makes it very hard to make money and continue their journeys."

Others are robbed before they get very far at all. One man who had a decent case for asylum, having worked as a translator for Australian forces in his home province of Uruzgan, is now stuck in Quetta after paying $40,000 to smugglers, who took him to Karachi then abandoned him.

The huge fees mean that most would-be emigrants are rich by Afghan standards, many having done well in post-Taliban Afghanistan. "I have people from all corners of Afghanistan, but most of them come from Kabul because they are rich," said the Jalalabad-based smuggler.

For a passage to Australia, another popular destination, the smuggler offered an all-expenses-included trip for $11,500. Like others in his trade he recommended Australia, promising it was a soft touch on granting asylum.

"Australia gives citizenship if you have a good story," he said. "I am 100% sure that after spending six months in a [processing centre] in Australia you will get citizenship if you do not lose your temper and have warning documents from the Taliban saying you can't live in Kabul."

He also trains his clients to stick to their story: "They will know you are lying, but as long as you say the same thing whatever they ask you, you will be fine."But the route to Australia is one of the most treacherous. After flying to Malaysia legally, the migrants move across the porous border into Indonesia from where they try to sail to Australia, if they are not caught by the Indonesian authorities and put in grim detention centres where they can remain for years.

Half of the migrants in limbo in Indonesia are Afghans, the UN says, with the flow increasing in recent years. Around half of those who get caught on the way eventually opt to go home rather than endure years in an Indonesian detention centre.

If they avoid getting caught they will try to travel on small, often overloaded, boats to Christmas Island, an Australian territory just 200 miles south of Jakarta.

One Quetta-based smuggler, Abdul Khaliq Karbalay, is currently advising would-be clients to wait as the route has become unusable in the wake of the sinking of a boat full of migrants off Java's east coast in December. Around 250 people were aboard but only 47 survived. Of them, only one asked to be repatriated back to Afghanistan. "Try again in 10 days," the smuggler suggests.

For Mohammad, a 30-year-old mechanic from Parwan province, finding the cash to travel is almost impossible. But he wants to leave because he thinks he will escape poverty if only he could work in Australia.But as an ethnic Hazara he is also concerned the future my see the return of the Taliban. The movement orchestrated the slaughter of Hazara men in the northern city of Mazar-e-Sharif in 1998. "I only survived by hiding in a house that the Taliban thought had been searched," he said. "I believe that when the Taliban come again they will start killing Hazaras.""I am worried about the future of Afghanistan," he said, pointing off into the distance at the wall of snow-capped peaks that surround the Afghan capital. "The Taliban are behind those mountains; they can come tomorrow or the day after."

Additional reporting by Nooruddin Bakhshi