The file in the Swedish National Archives is just one of thousands which contain the bones of an ugly secret. It was 1960. A 17-year-old woman lived a lifestyle that would raise few eyebrows today. She was in a motorbike gang in western Sweden.

She is described as being "without good judgment" by the doctors who examined her. She had no obvious "concept of ethics," they said, and they were sure that she was sexually active.

The teenager was sterilised, under a nationally-organised system in operation since 1935. Some Swedish teenagers were being sterilised by the state so that they would never have the children that the state did not want, for social, moral or racial reasons. There is nothing on the file to indicate whether this woman consented to the surgery.

The unnamed teenager was one of 62,000 people, 90 per cent of them women, who were sterilised in Sweden between 1935 and 1975. The practice, which predated and outlived Nazi Germany, started as an attempt to weed out perceived genetic weaknesses, mental or physical defects and ended as a method of social control.

In the worst years covered by the Swedish Sterilisation Act, the weak, the poor, the "feebleminded", the gypsies and even those who did not fit the image of the desired Swedish physique were not allowed by a big brother government to breed.

The revelation of details of cases by the newspaper Dagens Nyheter has shocked a state that prides itself on being a model humane society.

The Minister for Social Policy has announced the setting up of a commission to investigate the era. And those people sterilised against their will are looking for compensation.

One of the most disturbing revelations is that the Swedish policy continued for 30 years after 1945. Nazi Germany had taught the world all it needed to know about the evils of the idea of a genetically-engineered master race. Sweden's policy-makers and medical profession continued to play God until the mid-1970s.

In a phrase reminiscent of the grotesque "ethnic cleansing" seen in former Yugoslavia, Sweden pursued its policy of "ethnic hygiene" with Teutonic efficiency. Maija Runcis, a doctoral student who spent eight years researching the era, has studied about 5,000 case files which she came across while working in the archives.

The documents show a disturbing picture of a system tacitly accepted and facilitated by ordinary Swedish people. Its victims were the powerless and the marginalised not in a position to object.

Each file starts with a form applying for permission to have the person sterilised. This could come from a relative, social worker, teacher, politician or even a neighbour. "These people would have the application forms in their possession, fill them in and send them to the Medical Board," said Ms Runcis.

There would also be a doctor's report and often results of intelligence tests. "They would ask questions like: name the king of Sweden, what is the population of some city and where in the country is another city. They were ridiculous questions. I can't answer some of them."

The medical board, in Stockholm, would assess the applications. A single official, invariably a man, would finally sanction the operation. "They made about 20 decisions a day."

The most disturbing cases Ms Runcis found were those of the teenagers, some as young as 15, who accepted sterilisations in return for a release from a children's home or special school. "It was a form of blackmail and these people didn't have any choice," she says.

These sterilisations peaked in the 1930s and 1940s when the majority of victims were teenage orphans, some of them with mental or physical disabilities but others classified "rebellious".

"In the 1950s and '60s abortion law was very connected to sterilisation law. Women were often forced to sign documents allowing sterilisations to get an abortion."

Ms Runcis believes the policy was based on the pseudo-science of eugenics, but it then became a way of applying scientific solutions to society.

"At the beginning it was to do with race biology. After the war it was more to deal with social problems."

She finds the shock that has greeted the story ironic. "Nowadays people are appalled but before no one cared about these people."

The thousands of dusty files represent what she calls "a backyard to the Swedish nice little home. Everyone always talked about the Swedish model - how nice it is in Sweden. No one talked about things like this."

The Swedish Institute for Racial Biology was set up in 1922, according to Prof Gunnar Broberg, whose research into Swedish eugenics policies attempts to explain the method behind the apparent madness. In the first half of its existence the institute was heavily involved in propaganda, much of it fascist and based on German ideas of the Aryan race. "They held lectures on everything from how to breed good cattle up to risks for the Aryan race, given by German speakers in the 1930s."

Sweden passed the Sterilisation Act in 1935.

"The idea was not to allow the feeble-minded to give birth to children and to allow doctors to make that decision," says Prof Broberg. The law did not permit forced sterilisations, but in practice the issue of consent was clouded.

"Young girls were told they would be set free from homes and prisons `if we are allowed to make you calmer.' "

The policy was first introduced by the leftwing Social Democratic government, which opposed Hitler's ideology of the super race.

"Historians would argue that this is not just a result of the climate or zeitgeist of Nazism. These policies were introduced by those who took a stance against the Nazis. It was inspired by western science and the belief in large-scale experiments with man."

Its primary aim was not to produce a Nordic super-being, Prof Broberg argues. Rather it was based on the belief of male scientists that medical science held the answers to all Sweden's problems.

"It seems as if many people are shocked because Sweden has the reputation, at least among ourselves, of having a very clean history. The welfare state had taken care of the small people and we had a very humane society."

The medical board which sanctioned the sterilisations never met the people, but vetted the applications on paper. Much of the later applications were based on moral judgments, with doctors insisting on sterilisations for young women who were seen as unruly and promiscuous.

"It was a climate characterised by sexism and racism" and, it seems, an all-powerful paternalism that the state knew best. "There was an enormous belief in what science and genetics could do."

Since the Swedish revelations, other apparently "clean" countries have found similar skeletons in their cupboards. Both Norway and Denmark had similar policies.

And this week a Swiss history professor, Hans Ulrich Jost, said Swiss doctors sterilised mentally-handicapped patients (again most of them women) against their will under a law passed in 1928. "Even Hitler requested a copy of the law from the canton and from the government in Berne as a basis for Nazi Germany's own racist laws."