I SOMETIMES wonder why we call them “leaders”, when the evidence suggests that most politicians are remarkably slow to catch up with popular opinion. Take, for example, the EU’s “emergency summit” on migration, which has been convened just as immigration from illegal crossings of the Mediterranean and asylum claims have reached their lowest level for years.

The impetus for these talks is not the genuine refugee crisis that faced European countries several years ago, when Angela Merkel blithely introduced an open-door policy that has seen about 1.4 million migrants arrive in Germany since 2015. That, incidentally, created a huge upsurge in human trafficking, deaths at sea and an enormous headache for the southern European countries, especially Italy, to which many migrants headed. While that was at its peak, Mrs Merkel carried on as if there were no problem.

Now that she is dependent on her coalition partners, the anti-immigration Christian Social Union, it’s her political prospects that are in danger rather than piffling matters such as the lives of refugees or the cultural stability of Europe. The issue has naturally become much more pressing. It’s par for the course, I suppose, that the political priorities of the leader of a comfortable Western country should trump (I use the word advisedly) the desperation of those who come from places torn apart by war, governed by oppressive regimes, or devoid of opportunities to make a decent living. Yet migration has become a uniquely divisive issue, for reasons which often seem thoroughly irrational.

The EU summit has already been boycotted by four EU countries – the Czech Republic, Poland, Hungary and Slovakia – where immigration is a significant populist issue, while Italy has produced proposals which aim to end the link between a migrant’s point of arrival and the responsibility for dealing with his or her asylum claim.

Given that Italy has had to deal with the results of Mrs Merkel’s implied “come one, come all” rhetoric, that’s understandable but it will horrify other EU leaders, many of whom face growing electoral discontent over immigration. It could also create further problems for freedom of movement within the EU – one of the “four fundamental freedoms”.

In fact, despite Schengen’s supposed guarantee of free movement, the migrant crisis has already led to internal restrictions despite the EU’s objections; border controls were instituted between Denmark and Sweden for several years.

Yet the EU’s talk of freedom of movement, rather like its talk of its single market, disguises the underlying problem, which is that neither its movements nor its markets are in any sense genuinely free. On the contrary; they are protectionist measures which create barriers to those outside (which means, of course, most of the rest of the world, and the developing world in particular).

Before the First World War, in a world of many more borders and nation states, there were few obstacles to travel and resettlement, passports and border controls were a rarity and naturalisation for longstanding residents was a mere formality. The United States, where Donald Trump is disgustingly and dishonestly weaponising debate on the subject, owes its existence and success entirely to immigration.

Part of the reason this approach is working with so many Trump voters, and is also gaining support for similarly unsavoury populists such as Marine Le Pen in France and Viktor Orban in Hungary, is, it must be said, the reluctance of Western political elites to countenance discussion of the issue, and their implication that anyone who raises concerns about immigration is a racist. It’s only eight years, remember, since Gordon Brown airily dismissed Gillian Brown, one of his own supporters, as a “bigoted woman” for raising the matter.

The reason this attitude was so dangerous was that it concealed the facts about immigration and conflated the issue with a quite separate one, which is to do with multi-culturalism and globalisation. Racism in Britain, though it certainly exists, is fortunately confined to a (dwindling) minority.

Immigration, despite the noise about it, is also a minority concern, even among Leave voters; not a single poll found it cited as the major factor in the Brexit referendum.

But it is a very bad thing that it has not been properly discussed, because the evidence in favour of immigration is overwhelmingly positive, while the objections to it are largely about issues such as integration, welfare, schools and the provision of social housing.

Immigrants contribute considerably more to the economy than they cost (one report found European Economic Area migrants put in 34 per cent more in tax than they claimed in welfare payments). One obvious example of their contribution is the NHS, where more than one quarter of the doctors employed are from overseas. One consequence of Theresa May’s misinterpretation of Brexit (which she opposed) as being primarily about immigration (which most Leave voters did not list as a priority) is to endanger not only healthcare but also all manner of other areas of our economy.

Agriculture, education, and the technology sector, for example, are all highly dependent on migrant workers or overseas students. And the decline in the birthrate in Western countries, and their ageing populations, ought to make importing people to contribute to pensions a priority.

What’s more, a welcoming approach towards immigration ought to be the natural position for a party which claims to support economic growth, a free society and open markets. From a truly liberal perspective, immigration policy shouldn’t even be a matter for the Government but for the market. After all, if people choose to come to the UK, it is because they see it as an opportunity for themselves and their families and, if they choose to stay, they become British anyway.

Businesses and immigrants themselves are best placed to determine whether migration is in their mutual interest, which is why the idea of having some number plucked from the air, with no reference to need or desirability, fixed as a cap is absurd. The Home Secretary’s announcement that the default position of the UK would be to grant settled status to EU nationals living here was welcome, if belated, but did not go far enough.

Politicians should be making the case that immigration is not a problem but a boon, while populist rhetoric about crime or welfare should be rebutted vigorously. If the EU leaders have not wanted to discuss the issue until now, the least they can do is point out that the facts disprove the claims of those opposed to immigration.