THERE IS supposed to be debate about immigration. It’s certainly passed me by. A debate pits one set of ideas against another. But when it comes to immigration, all sides agree on the fundamentals: there are too many immigrants entering Britain, many are feckless scroungers and we need more robust controls. The only “debate” appears to be about how best to keep them out.

The one question that could spark a proper debate is one that no one seems willing to ask: why do we need to control immigration at all? The idea of throwing open our borders would undoubtedly strike most people as mad. That’s only because no one has challenged the myths of immigration that are used to justify controls.

Myth 1 “If we have an open door the whole world would walk in.” It’s obvious, isn’t it? Britain is rich, much of the world is poor. Open the borders and the hordes would descend upon us.

Well, actually, they wouldn’t. Given the great global disparities of wealth, what is striking is not that so many people move to richer climes but that so few do. Emigrating is not like going on holiday. You can’t just pack your bags and take the next easyJet flight out. You often have to abandon your family, your friends and the life that you know for an alien country with strange habits and where the people are often hostile. Those who do emigrate tend to work for a period, earn money and return home. And generally they’re not the poorest, but those who are better off, speak a foreign language and find it easier to make their way in an alien culture.

It is not an open border, but tight immigration controls, that make people move in large numbers and settle. In the 1950s, when Britain had a virtual open door, many of the initial immigrants were single men and women who expected to return home after a short time. Once the Government began discussing possible controls in the late Fifties migrants started arriving in larger numbers, to try to beat the closing door. And once the 1962 Immigration Act came into force they had no choice but to settle here and bring their families over, because they knew that if they left they might never get back in again.

Open borders allow people to move in and out according to need. Closed borders compel people to settle, even if they have no desire to.

Myth 2 “They take all our jobs.” OK, say the critics, even if the whole world doesn’t want to come here, those immigrants who do come deprive indigenous workers of jobs because they provide cheap labour. Wrong again. Migrants don’t take jobs away from local people; they do jobs that locals won’t do or can’t do. Two years ago the Home Office commissioned an independent report on the impact of immigration on local workers. The report looked at international surveys and conducted its own study in Britain. “The perception that immigrants take away jobs from the existing population, or that immigrants depress the wages of existing workers,” it concluded, “do not find confirmation in the analysis of the data laid out in this report.”

Myth 3 “They’re a burden on the welfare state.” The people who make most use of state services are the young and the old. Those aged between 18 and 60 generally have less need of hospitals, schools and benefits, but still pay taxes. Almost by definition, migrant workers fall into this category. The “benefit tourist” is largely to be found in the imagination. Some 90,000 East Europeans came to Britain last year in the first five months after EU enlargement in May. Just 15 claimed any form of benefit. Only someone who has never had to claim benefit could suggest that Britain’s social security system is an easy touch for foreigners.

Perhaps the biggest myth of all is the idea that a government can control immigration. Take, for instance, the Tory plan for an annual quota on economic migrants. Will there be some bureaucrat sitting in a Ministry of Silly Numbers deciding that we will let in 1,417 strawberry pickers and 586 steel erectors next year? And what happens when we need extra pickers and erectors? Will the Government say to employers, “tough, you’ll just have to sell less fruit and build fewer houses”? Or will employers continue, as now, to rely on illegal workers who are forced to labour in appalling conditions, for derisory wages and with no legal protection?

I’m no free marketer. I believe that the introduction of market forces into the NHS and education has had a disastrous impact. But the notion that governments are best placed to predict labour demand and hence regulate labour flow is a fairy tale. However, when it comes to the question of immigration, the apostles of the free market on both sides of the political spectrum suddenly become cheerleaders for the policies of a command economy.

For all the myths about immigration, what really drives the debate is not concern about anything so tangible as jobs or benefits. Rather it is a sense of fear — a fear that Britain is changing, identities are eroding and communities are disintegrating. And immigrants have become the scapegoats for this. Yet even if no immigrant had come to Britain, we would still be living in a vastly different nation from half a century ago. Feminism, consumerism, increased mobility, greater individual freedom, the decline of traditional institutions such as the Church — all have helped to transform Britain, sometimes for better, sometimes for worse. It’s immigrants, however, who now get the blame for all our social ills, but little credit for the benefits that they have brought us.

Kenan Malik’s film Let ’Em All In is on Channel 4 tonight

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