Author and economist Philippe Legrain argues for the free movement of labour, but would this model work for Ireland?

The argument against immigration is the last refuge of racism in polite society and removing all border controls would substantially boost the world economy, perhaps even doubling it. This is one reading of Philippe Legrain's views, which are laid out in his book Immigration: Your Country Needs Them, which was shortlisted for the FT Business Book of the Year Award and that has positioned him as a leading commentator on this most divisive of topics.

Legrain is an alumni of The Economist's school of liberal capitalism. He wants complete freedom of movement in the labour market, just as there is in capital markets.

Countries such as Ireland, which he says has moved from "a country of emigration to one of immigration within a generation", would benefit hugely from a more liberal approach to border controls.

The influx of foreign workers in to Ireland has already been of enormous boost to the economic prosperity of all and is a defining characteristic of the Celtic Tiger. It is natural and desirable that as the level of education in advanced countries improves, so the lower skilled jobs are filled by people from less privileged countries.

He points out the paradox that labour movement among white, middle class members of the thought economy is routinely lauded. If you are a banker, lawyer or computer analyst it is expected that New York, London, Silicon Valley, and increasingly Dublin, will be where you pitch for work. That this does not apply to lower skilled workers is based in part on racism and is a "form of global apartheid", he says.

Legrain uses his economic background to question some of the received wisdoms of the anti immigration lobby. First of these is that the presence of low wage migrants reduces the wage levels of all unskilled workers. "They do the jobs Irish people do not want to do, which is the trend in all advanced economies around the world".

He also rejects the notion that a significant influx of foreign people undermines the tax and welfare state systems. The closest Legrain comes to accepting the social problems relating to integration is to suggest that many be allowed in on a temporary basis or that the law attempt to formalise the payments they make home.

Economics only goes so far in this debate, however, which very quickly becomes more emotive than rational. "The problem is that the economic argument for free movement of people has been entangled with the debate on terrorism," Legrain tells The Irish Times. Since 9/11 there has been a greater tendency to dismiss foreign workers as "an invading army".

He says that there are marked differences in the way Poles have been integrated into British and Irish society since the expansion of the EU in 2004 than people from muslim countries. "Polish and other eastern Europeans have become valued members of society, making a huge cultural as well as economic contribution to the country."

Immigration controls are essentially useless at keeping people out, he says. No country in the world can hope to police every inch of their borders. Politicians know this well, but few will acknowledge the fact. By allowing free access, money will flow from the rich countries back to the poor ones. "The money sent home by people working abroad outstrips by two or three times the amount given to poor countries in aid."

This was true of Irish emigrants as it is of those from China, Poland or Somalia. In addition to hard cash, the skills and knowledge gained by those working in the west will also filter back to home, in a more seamless and efficient way than aid agencies or the UN could hope to replicate. Africa's first internet cafes were started by people returning home from the west.

However, it is the humanitarian cost of immigration controls that are the most important to Legrain - the suffering of people held in detention centres, or who die escaping totalitarian regimes, the growing underground industry of human traffic. Harsh immigration controls don't stop people coming in or staying beyond their allotted time, they drive them underground, making them more vulnerable to criminals and out of the reaches of the formal economy, he says. Politicians who propose greater protection do so to garner votes from people fearing a breakdown in law and order in society.

This is fundamentally flawed, says Legrain, because such controls serve only to undermine law and order. In the rush to offer the "the illusion of protecting our borders" the much cherished freedoms enjoyed by all are reduced, making us more suspicious of foreigners and more insular.