Leading article: Demographic trends that speak well of Britain

Not so long ago, forecasts that the UK population could reach 65 million within 10 years and 70 million by 2031 would have been greeted by calls for voluntary limits on the size of families and a clamour for more education about birth control. It was quite clear, after the release of these projections by the Office for National Statistics yesterday, however, that it was not the family-planning lobby that would seize on them first, but those concerned about immigration.

And so it was. Sir Andrew Green, chairman of Migrationwatch, spoke in characteristically emotive terms, when he called for immediate action to limit the number of people settling in the UK. "This huge population increase," he said, "– equivalent to twice the population of greater London by mid-century – is 90 per cent due to immigration." He raised the spectre of a Britain that would be "irrevocably and permanently changed".

Population figures, whether they suggest a steep rise or precipitate fall, can be relied upon to incite passions. The notion that a country must accommodate many more people in the future, or somehow manage without the numbers it is used to spreads apprehension about social upheaval beyond individual or government control. Yet there are many reasons why alarmist language should be avoided.

The figures released yesterday are only projections. There is no guarantee that the population will increase at this pace or in this way. Models of population growth proceed from assumptions that can be wrong. It is unlikely, for instance, that immigration will continue at the rate of the past 10 years. Free movement in the enlarged European Union was a one-off change. It is being accompanied by far more rigorous entry criteria for would-be workers from outside the EU.

Nor can we be sure what proportion of recent EU arrivals will make the UK their home. As living standards and job opportunities in the "new" EU countries rise, many of Britain's additional workers may choose to return. The number of asylum-seekers has already fallen in response to a toughening of requirements. The number of Britons emigrating or retiring outside these shores may also decline, as other countries impose health insurance requirements (as France has recently done) or the attraction of foreign destinations palls.

Fertility projections can also prove fallible. While first-generation migrants tend to have larger families than the indigenous population, this is not true of second and subsequent generations, whose family patterns are more likely to resemble those of the country they have joined. There are therefore many uncertainties surrounding the ONS figures.

Even if we accept, however, that they present an accurate picture of where the UK is heading, is there so very much to be feared? The value to this country of a larger tax base and a livelier domestic market should be evident. A study published last week suggested a net gain to the UK economy of £6bn. The cost – in terms of additional infrastructure and services – is harder to assess. The consensus is that, at very least, there is a small net benefit from immigration.

Nor is it true to say that the UK is a small country with no room for any more people. Population growth is projected for all regions of the country, not just for the congested South-east. And the housing shortage, such as it is, has to do as much with land use and clumsy planning mechanisms as it does with population growth.

Instead of grumbling about the problems that might accompany a larger population, we should hail the opportunities. If the birth rate in Britain is rising and migrants compete to make their future here, this is a vote of confidence, and it should be a point of pride.