A British exit from the European Union would be very bad news for Ireland. Voters in the U.K. will vote on the “Brexit,” as it’s known, at a referendum on Thursday, June 23.

The worst case scenario would see tariffs go up between the trading partners. About 16 percent of Irish exports go to Britain, a figure that is probably on the low side given the distortion of export numbers by U.S. multinational repatriation policies.

The opinion polls show that Britain right now would remain in Europe, but the numbers are by no means home free with a seven to 10 point gap between those who want to stay and those who want to leave.

Such numbers can change in the middle of a campaign, especially one as hard to adjudicate as this. There has never been the same warmth towards Europe from Britain as there is from Ireland, and that is unlikely to change.

The real disaster could be the re-installation of border checkpoints and customs the length of the Irish partition line.

The psychological reality of a return to the bad old border days with the opportunity for violence by paramilitaries and others would be very real.

British Secretary of State for Northern Ireland Theresa Villiers has been disingenuous on this issue, pronouncing herself one of the most high level supporters of exiting the EU while assuring the Irish it will not result in bringing back the border.

She seems caught in a paradox and is not the most suitable British representative in Northern Ireland at this point.

While unionists might initially welcome the return to the good old isolationist days, their businesses would also be deeply affected by lengthy delays, not to mention losing huge EU subsidies in the agricultural region.

It is worrying, however, to see Northern Ireland First Minister Arlene Foster, who has just taken over the job, display a clear favoritism towards her own side at every opportunity. Recently when naming Northern Irish towns she made a point of not mentioning any with nationalist populations.

She also refused to attend the American Ireland Fund dinner in Washington, D.C. this week, absurdly deeming the organization too green -- which is like calling Barack Obama too black to deal with. Her refusal to get on with governing is distressing to say the least, and Brexit might give her another opportunity to vacillate.

So worried are the Irish government that they have begun to urge the Irish in Britain to influence their fellow emigrants to vote against Brexit as a matter of urgency.

On the face of it, the Brexit supporters should lose, especially with a concerted campaign by British leader David Cameron and improved deals with the EU.

But let’s not forget it was Cameron himself who mooted holding the referendum to begin with, and unintended consequences may well occur.

The notion of Northern Ireland stepping back into its cheerless past with border lines, currently non existent, redrawn again is very damaging indeed.

Let us hope that the people of Britain feel the same way. If they don’t we will have yet another crisis in the North on our hands.

Don't believe a word that if Brexit passes on June 23 it will have no impact on British/Irish relations.iStock