Precise immigration numbers are essential

Good data is an essential prerequisite to a mature debate on this emotive topic

As immigration is perhaps the most potent issue in British politics today, it is very important that the debate about it should be informed by the most detailed and trustworthy data that can be obtained. Parliament’s Public Administration Select Committee was therefore right to complain yesterday that official UK migration figures are “little better than a guess” and were “not fit for purpose”.

Bernard Jenkin, the committee’s chair, said the sample was too small and the margin for error too large. Yesterday Vince Cable made the additional point that net migration was a “misleading” indicator because it quite wrongly counts students as immigrants.

But Mr Cable then went on to describe the urge to count migrants precisely as “totalitarian”. That is absurd: is a properly conducted national census a totalitarian measure? If, as opinion polls tell us, many of us are deeply concerned about immigration, there is every reason to count people in and out as precisely as possible. The UK remains outside Schengen, so why, unlike other countries with supposedly robust border controls, are there no longer any checks by the Border Agency on the passports of those leaving? It is a bizarre omission.

Another area where information is very hazy is the scale of illegal immigration, for by definition illegal immigrants do not stand around to be counted. This allows scaremongers in Ukip and other right-wing fringe parties to spread alarmist rumours about the size of the problem. And this in turn, it seems, has encouraged the Home Office to counter with its grotesque “In the UK illegally? Go home or face arrest” publicity campaign, trailed over recent days in six London boroughs.

More knowledge is the essential prerequisite to a mature national debate about this emotive issue. One sure way to acquire it would be to adopt Boris Johnson’s proposal of a one-off amnesty for illegal immigrants. This would not only clarify the situation, it would also be a welcome humanitarian initiative in its own right.