I came back from holiday in the vast calm of Burgundy to find that the UK will have the largest population in Europe by 2060, on half the land area of France. Sharif told me this while he was doing my hair. He thinks it would be “crazy, darlink, so sweaty, and just not fair”. But he also worries that his Polish builders will go home and leave him with Albanians who are less cute and who have apparently acquired the English tea-break mentality, but not much English.

We have become completely contradictory about migration. We are alarmed by the numbers of people reaching these shores, yet suddenly afraid that they might pack up and leave. Can we afford to lose energetic people who have helped to drive the economy? Can we afford to keep them? How many is too many?

First, the stats. If there is any certainty at all in population projections, it is that a 50-year EU projection is bound to be wrong. So I dug out the Government's 20-year forecast. It's stunning. The Office for National Statistics expects Britain's population to rise by ten million, seven million from immigration. That would require the building of ten big cities. Yet the Government has no plan for housing the numbers it is apparently planning to accept, nor for providing the services they would need. Already, half the babies in London's maternity wards have foreign-born mothers. That doesn't make any baby worth any less. But those of us who have given birth in the capital in recent years know that midwives are dangerously variable in quality and that hospitals are so overstretched that women are being turned away from hospital to give birth on the kitchen floor.

Will a recession empty the wards and leave our dynamic economy bereft of talent? Probably not. The significance of the Polish exodus has been overblown because of the assumption that Eastern Europeans are a majority of those coming here. Yet they have never been. Even in 2004, when the Government opened Britain's doors to the new EU accession countries, of the 940,000 people who came here legally only a third were from the EU. Over the past 15 years more than 90 per cent of legal arrivals have been from non-EU countries.

This gives the lie to the pretence that the Government cannot restrict the numbers entering Britain. The fourfold rise in official immigration in the past decade can be explained largely by deliberate policy. In 1997 the abolition of the Primary Purpose Rule removed the restriction that required applicants to show that they were not just marrying to enter the UK. In 1998 the abolition of embarkation controls ended any effective record of who came in and out. In 2002 the number of work permits was doubled. The Government now claims to have created an “Australian-style points system” to keep out the low-skilled, but it is Australia-lite. Australia sets an annual limit on numbers, then takes those with the most points. The British have no such limit.

Much of our contradictory approach is because while we appreciate the undoubted skills of foreign doctors and builders, we are less enthusiastic about handing out lifetime entitlements to unprecedented numbers of people merely on the basis that they are here, legitimately or not. It is clear that immigration has brought much-needed wealth, ideas and energy into the British economy. It is less clear, over time, how to balance economic benefits against the value of state ones.

The answer may be to decouple the two. There is no cast-iron reason, for example, why immigrants who have been here for five years should automatically acquire a permanent right to remain. Nor is it axiomatic that they should have the same entitlements as British citizens. Many countries with open borders refuse to give immigrants equal rights. When I lived in Bangladesh I met many families whose income came from guest worker relatives in Kuwait and Jordan. During the Gulf War, the sheer number of disgruntled returnees astonished me. For me, the term “guest worker” was flush with imperial exploitation. But these people were just grateful that they could earn. They did not expect additional benefits. They were keen to get back, even to Singapore - which expels guest workers if they become pregnant.

The guest worker concept is unpalatable in many ways. But it may be fairer than shutting people out altogether. The US economist Lant Pritchett has called guest work a liberal solution to the problem of the “irresistible forces of global migration” coming up against the West's “immovable ideas” of nationhood.

I raise the issue because it seems clear to me that our current approach is both undemocratic and unsustainable. When the official figures point exponentially upward - and the official figures are a woeful underestimate because they fail to capture the illegals - we are in danger of stretching the social contract to breaking point. People are getting angry, and they will get angrier if the recessionary tide leaves ever more foreigners claiming benefits here.

The alternative to a guest worker system, which feels more British, would be to offer every legitimate worker equal rights - to benefits, at least, if not to permanent residency. But in this overcrowded island, this will only work if there is some kind of cap on numbers. Come to Tower Hamlets and see people living eight to a room. Spot the secret doors cut into buildings which have been divided up into grim tenements, like the old Jewish ghettos. Many of these people earn below the minimum wage and some are trafficked. It is inhuman.

I believe we face a choice: between open borders and guest workers, or closed borders and fewer workers. To continue to pretend that we do not, as recession looms, may prove politically dangerous. The immigration issue is now spatial, not racial. And the fairest solutions may be those that look the least liberal.

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