UK exit from EU would take big toll on Border area

Obviously if the UK leaves the EU, it would negotiate some sort of new relationship with it. All sides will agree on that because half of British exports go to the euro zone.

But what sort of relationship? One of the big drivers of anti-EU sentiment in Britain is immigration of EU citizens from central and eastern European countries, like Romania, Bulgaria, and the Baltics. Gordon Brown famously encountered this sentiment during the last British general election.

If the UK left the EU, it would indeed be free to bar immigration from particular EU countries. But, as a continuing member of the EU, the Republic could not do the same.

So if the UK wanted to prevent these EU immigrants entering the UK through the Republic, it would have to introduce passport controls at Newry, Aughnacloy, Strabane and on all other roads by which they could cross the Border from the Republic into the UK.

If the UK was outside the EU, tariffs would also have to be collected on UK exports entering this state. Average EU tariffs are quite low, but some tariffs, on items such as dairy products and clothing, are quite high.

Customs posts would have to be placed on Border roads to ensure collection of these tariffs. Smuggling, with all its potential as a funding source for other forms of illegality, would become very profitable again.

But the human and political cost in the Border counties would be the worst aspect of it. Nationalist communities would again feel cut off from the Republic by the inconvenience of passport controls, and the efforts to market Ireland as a single tourist destination would be set at naught.

Some might say that these risks could be mitigated if the UK negotiated a deal with the EU like those of Norway or Switzerland, including free trade and free movement of people .

Apart from the fact that this would not satisfy British anti-immigration sentiment, to have duty-free access to EU markets for its goods and services Britain would have to continue to apply EU rules, as now, but without having had any say in them.

This is what Switzerland and Norway have to do. Britain would also have to continue to contribute to the EU budget, as Norway does. That would be even more annoying to British Eurosceptics than the present situation. Complete UK exit is therefore a real possibility.

The Irish diplomatic service should intensively brief all British MPs well in advance of the next UK election on the dangers of setting off a train of events that could lead to an exit of Northern Ireland, along with the UK, from the European Union.

JOHN BRUTONis a former taoiseach and former EU ambassador to the US