They will be searching their souls in Stockholm tonight. And in Oslo, Helsinki and Copenhagen, too. All over Scandinavia, people are facing up to the stain now spreading across their snow-white self -image, as they discover that their governments spent decades executing a chilling plan to purify the Nordic race, nurturing the strong and eradicating the weak. Each day victims of forced sterilisation, now deep in middle age, have stepped forward to tell how they were ordered to have “the chop”, to prevent them having children deemed as racially defective as themselves.

Branded low class, or mentally slow, they were rounded up behind secure fences, in Institutes for Misled and Morally Neglected Children, where they were eventually led off for “treatment”. One man has told how he and his fellow teenage boys planned to run away rather than undergo the dreaded “cut in the crotch”. Maria Nordin, now seeking compensation from the Swedish government, remembers sobbing as she was pressed to sign away her rights to have a baby. Told that she would stay locked up forever if she did not cooperate, she relented – spending the rest of her life childless and in regret.

In Sweden the self-examination has already begun. A government minister has admitted that “what went on is barbaric and a national disgrace”, with more than 60,000 Swedish women sterilised from 1935 until as late as 1976. What has shocked most observers is that all this was committed not by some vile fascistic regime, but by a string of welfare-minded, Social Democratic governments. Indeed, the few voices of opposition came from Swedish conservatives.

But the reckoning cannot be confined to Scandinavia: Britain has some soul-searching of its own to do. What’s more, as in Sweden, the culprits are not long-forgotten fire-breathers of the far right. On the contrary: eugenics is the dirty little secret of the British left. The names of the first champions read like a roll call of British socialism’s best and brightest: Sidney and Beatrice Webb, George Bernard Shaw, Harold Laski, John Maynard Keynes, Marie Stopes, the New Statesman even, lamentably, the Manchester Guardian. Nearly every one of the left’s most cherished, iconic figures espoused views which today’s progressives would find repulsive.

Thus George Bernard Shaw could write: “The only fundamental and possible socialism is the socialisation of the selective breeding of man”. Later he mused that “the overthrow of the aristocrat has created the necessity for the Superman”. The revered pacifist, disarmer and philosophical titan, Bertrand Russell, dreamed up a wheeze that would have made even Nazi Germany’s eugenicists blush. He suggested the state issue colour-coded “procreation tickets”. Those who dared breed with holders of a different-coloured ticket would face a heavy fine. That way the high-calibre gene pool of the elite would not be muddied by any proletarian or worse, foreign, muck. The New Statesman agreed, explaining in July 1931: “The legitimate claims of eugenics are not inherently incompatible with the outlook of the collectivist movement. On the contrary, they would be expected to find their most intransigent opponents amongst those who cling to the individualistic views of parenthood and family economics.” The bottom line is bleak but clear. Eugenics, the art and science of breeding better men, is not just the historical problem of Germany and now Scandinavia, nor even of the jackbooted right. It took root right here in Britain – pushed and argued by the left. Indeed, contempt for ordinary people and outright racism were two of the defining creeds of British socialism.

The trouble began with Charles Darwin. His breakthrough work, The Origin of Species, did not restrict its impact to the academy and laboratories. Instead it transformed the very way mankind understood itself in the 19th century, its message fast spilling over into the realm of political ideas. Suddenly the religious notion that all life was equally sacred was under attack. Human beings were like any other species – some were more evolved than others. The human race could be divided into different categories and classes. When Karl Marx took on the task of charting human development and defining the class structure, he acknowledged his debt – dedicating an early edition of Das Kapital to none other than Charles Darwin.

From the beginning, socialism regarded itself as the natural ally, even the political version, of science. Just as biologists sought to understand animals and plants, so scientific socialism would master people. According to Adrian Wooldridge, author of Measuring the Mind: Education and Psychology in England 1860-1990, and a recognised authority on early ideas of human merit, progressives believed the only enemies of Darwin were reactionaries, the religious and the superstitious. Science, by contrast, represented progress. Crucially, these early leftists regarded science as an utterly neutral tool; something could not be scientifically right and morally wrong. In this climate, says Wooldridge, “eugenics became the political correctness of its day”. If you were modern, you believed in it.

The result was a Darwinian commitment to improving the quality of the nation’s genetic stock. Many of the reforms admired by today’s leftists were not, in fact, borne of a benign desire to improve the lot of the poor, but rather to make Britons fitter – to guarantee their survival as one of the globe’s foremost races. Thus the Webbs pushed for free milk in schools not because their hearts bled for undernourished kids, but because they were alarmed by Britain’s performance in the Boer war, where troops had taken a good kicking at the hands of the black man: the Webbs believed a daily dose of calcium would improve the bones and teeth of the future working class.

The contemporary left has a similarly misguided and sentimental view of Marie Stopes’s campaign to bless the women of King’s Cross and the rest of working-class Britain with contraception. The unrosy reality is that Stopes, Mary Stocks and the like were not motivated by a kind of proto-feminism, but rather by the urge to reduce the numbers of the burgeoning lumpenproletariat. This rather awkward fact was exposed earlier this year with the release of a long-suppressed essay by the father of liberal economics, John Maynard Keynes. He endorsed legalised birth control because the working class was too “drunken and ignorant” to be trusted to keep its own numbers down: “To put difficulties in the way of the use of (contraception) checks increases the proportion of the population born from those who from drunkenness or ignorance or extreme lack of prudence are not only incapable of virtue but incapable also of that degree of prudence which is involved in the use of checks.”

Many progressives were drawn to the hope that science could build up the strong parts of the nation, and slowly eliminate the weak. Dozens of them signed up for the Eugenics Society, which in the 1930s rivalled the Fabians as the fashionable salon of London socialism. Labour MP Ellen Wilkinson even wanted the society to form its own committee of Labour sympathisers. HG Wells could not contain his enthusiasm, hailing eugenics as the first step toward the removal “of detrimental types and characteristics” and the “fostering of desirable types” in their place.

For these early thinkers, eugenic socialism posed no contradiction: indeed, it made perfect sense. As Wooldridge points out, “the Webbs supported eugenic planning just as fervently as town planning”. If socialism was about organising and ordering society from the centre, then its most extreme advocates believed in extending that control – all the way into the wombs and testes of society’s weakest members. What they wanted was a neat, clean, planned Utopia: eugenics was just one part of that dream.

One other doctrine was crucial – profound elitism. It strikes the 1990s ear oddly, but these leading lights of British socialism had no patience for equality. The communist and one-time editor of the Daily Worker, JBS Haldane, considered equality a “curious dogma … we are not born equal, far from it”. Many on the left were members of the upper middle-class or lower aristocracy, convinced their higher intellectual capacities had to be preserved from proletarian infection. One popular idea of the time was to encourage artificial insemination – not to help the infertile, but to impregnate working-class women with the sperm of men with high IQs. Beatrice Webb was sure her genetic material was worth preserving, describing herself as “the cleverest member of one of the cleverest families in the cleverest class of the cleverest nation of the world”. She and her fellow travellers envisaged a world run by an elite made up of people like her, able to determine who could reproduce and who could not. Always fond of gazing into the future, HG Wells pictured a caste of all-powerful super-talented Ubermenschen, who would wear Samurai-style dress, and order the affairs of the planet.

In this context, there was only contempt for ordinary people, who were regarded as “sub-men” to be tended and looked after – via the welfare state – like a bovine herd. The Labour cabinet minister Douglas Jay felt no embarrassment in putting the attitude on record in his pamphlet, The Socialist Cause. Famously and loftily he declared, “In the case of nutrition and health, just as in the case of education, the gentleman in Whitehall really does know better what is good for people than the people know themselves”. Non-Britons came even lower on the Darwinian pecking order. In those times it was the Jews who were regarded as posing the chief threat of alien dilution of English blood. Bernard Shaw described the Jews as “the real enemy, the invader from the East, the ruffian, the oriental parasite”. JA Hobson, a radical journalist who made his name covering the Boer war for the Guardian, declared that the Transvaal had fallen prey to “Jew power”.

For years, leftists, historians and everyone else have drawn a veil over Adolf Hitler’s naming of his creed National Socialism. It has been dismissed as a perverse PR trick of the Fuhrer’s, as if Nazism and socialism represented opposite faiths. The same view has infused the left’s understanding of the genocides committed in the name of communism, whether by Stalin or Pol Pot, as if those men were merely betraying the otherwise noble theory whose cause they proclaimed. But the early history of British socialism tells a different story. It suggests that socialism – with its unshakable faith in science, central planning and the cool wisdom of the rational elite – contained the seeds of the atrocities that were to come later.

Eventually, in the shadow of Auschwitz, Treblinka and Sobibor, the British left gave up its flirtation with eugenics. They saw where it had led. But, just like the governments of Scandinavia, their past was buried too quickly – and forgotten. The names of Russell, Webb and Shaw still retain their lustre – despite their association with the foulest idea of the 20th century. They escaped the reckoning. Perhaps now, posthumously, it’s time to see them, and much of socialism itself, as they truly were.