Of course Brexit would mean new border controls, insists Mandelson
Labour peer accuses Theresa Villiers of 'dodging reality' over impact
Lord Mandelson has accused Secretary of State Theresa Villiers of "putting her fingers in her ears" on the issue of Northern Ireland border controls.
A leading Brexit campaigner, Ms Villiers has consistently said there will be no new frontier checks with the Republic if the UK votes to leave the European Union.
But speaking to the Belfast Telegraph during his visit to Belfast yesterday, the former Northern Ireland Secretary accused her of ignoring reality.
"Theresa Villiers is saying that because it's an inconvenient truth that she wants to brush it aside," said the veteran Labour politician.
"Of course the border will change if Britain leaves the EU. It would be done to stop or control the free movement of people.
"It's not conceivable that leaving the EU for the purpose of controlling migration could be done while you are leaving the back door open in Northern Ireland.
"It would have to be policed, otherwise people would simply arrive in the Republic from other countries, come across the border and pass freely into the UK."
Lord Mandelson - who was also Business Secretary and a former European Trade Commissioner - said border controls would have a "very substantial impact" both politically and economically.
"The Northern Ireland economy has been transformed and one of the reasons for that has been allowing an all-island economy to grow," he said.
"Some 18,000 people every day cross the border for employment, as well as around 4,000 students.
"I'm not saying they would all be stopped, but passports and identities would have to be checked and we would be operating a different Customs area.
"Trade would be impeded, slowed up and more costly.
"People in Northern Ireland need to look at the economic facts and see where their prosperity comes from, and that is chiefly from trade with Europe.
"Those on the Leave side who claim that we could turn our backs on the EU but continue to trade in the same way on our own terms are either openly lying or indulging in a fantasy."
He also dismissed suggestions from some on the Leave side that the Republic may follow the UK out of the European Union.
"I don't believe that. Why would they trash their own economy just to leave the EU over the issue of the border with Northern Ireland?" he said.
"It won't happen."
During his time at the Northern Ireland Office, from 1999 to 2001, Lord Mandelson was heavily involved in negotiations to maintain the peace process. He believes a Brexit would damage what has been achieved and would have a major political impact across the UK's regions.
He added: "People are saying that the consequences could be fresh division in Ireland and a move towards separation in Scotland. It would certainly sound the death-knell for the stability that we have worked so hard for and which has delivered so many benefits for all of us.
"The chief price we would pay is economic, but there would also be political ramifications."