A FORMER British chancellor and a current junior minister have suggested border posts may have to be put back in place in Ireland if the UK leaves the EU.
Nigel Lawson, now Lord Lawson, said "there would have to be border controls" if the Brexit camp wins the June referendum.
His comments came as Tory MP Dominic Raab also said some “form of checks” may be needed if Britain leaves the EU and Ireland remains a member.
Mr Lawson served as a high-profile Chancellor of the Exchequer under former British Prime Minister Margaret Thatcher.
He is also the former interim chairman of the Vote Leave campaign.
Secretary of State Theresa Villiers, who is also campaigning to leave the EU, has claimed that border checks between north and south may not be necessary.
But speaking to the BBC’s Andrew Marr on Sunday, Mr Lawson confirmed there would be measures needed to control immigration.
“That can be stopped, there would have to be border controls but not a prevention of genuine Irish from coming in, from crossing the border,” he said.
He added that “there is now particularly close co-operation between the security services in Northern Ireland and the security services in the Republic to prevent the IRA and the terrorist threat from being worse than it is”.
During an interview with Sky News presenter Dermot Murnaghan on Sunday, Mr Raab - another supporter of the leave campaign - also responded to suggestions that passport controls may have to be put in place in Ireland.
“Well, we would have to look very carefully at that, we’ve got a bilateral relationship with Ireland, a very close relationship,” he said.
“We have also got the history of the Troubles. All of these things could be handled very sensitively.”
But he added: “If you are worried about border controls and security.... if you are worried about the effect of those EU rules, then you couldn’t leave a back door without some kind either of checks there with any country or assurances in relation to the checks that they are conducting, obviously, otherwise everyone with ill will towards this country would go round that route,” he said.
“So the truth is that the broader point here is that if you want to have safe borders, if we want to have proper checks to deal with terrorism and broader crime, you have to come out of the EU."
Earlier this year Theresa Villiers insisted there was "every reason to suggest" that the Republic and UK could maintain free movement.
Asked whether Brexit would mean tighter border controls, she said: "That's not inevitable at all. We've always had a much closer relationship with the citizens of the Republic of Ireland than with the rest of the EU.
"It's perfectly possible to maintain that free movement with Irish citizens. After all we give them privileges in the UK which we accord to no other EU citizens, like the right to vote in our elections."
The Northern Ireland Office last night directed enquiries on Mr Lawson's comments to the Vote Leave campaign.
A spokesman for the campaign claimed the former chancellor's remarks are not at odds with those made by Ms Villiers.
"The UK have had a common border travel area since the Irish Republic was formed and we expect that to continue," he said.
"We don't anticipate border controls being put in place between northern and southern Ireland."