FORMER US special envoy Richard Haass believes the UK should have a second vote on EU membership because first time around people did not understand the full impact of Brexit.
The diplomat, who chaired an unsuccessful round of all-party talks in 2013, told The Irish News that the realities of leaving Europe were not apparent when the referendum took place in June last year.
The potential for a second vote on EU membership was first raised by Leave campaigners ahead of last year's shock referendum result and has since been adopted by the Liberal Democrats and its sister party in the north, Alliance.
Earlier this week at the Labour conference, London mayor Sadiq Khan suggested his party may back a second referendum on withdrawal from the EU, a call also backed by the Republic's Labour Party and Fine Gael.
Mr Haass, who in the autumn of 2013 chaired ill-fated talks between Stormont's parties on flags, parades and legacy, said "nowhere is it chiselled in stone" that only one referendum should take place.
"The main reason (for a second referendum) is given how consequential it is – we are talking about something that will send the UK on a different trajectory" he said.
"This is not a policy but the country's future and given how consequential it is and how lasting its impact will be, I think you need to give the people another chance to weigh in – if they reaffirm it, so be it."
The president of the Council on Foreign Relations think tank argued that many of the claims by Leave campaigners in the run-up to the referendum were "incorrect or incomplete".
He claimed the realities of Brexit were now "much more apparent" and that the electorate needed a "second chance".
"When the vote was taken it was much more a symbolic vote – people that were voting to leave the EU were sending a message to the establishment, while for others it was reaction to immigration or misinformation but now we know a lot more."
Dr Haass said he believed Brexit would be "terrible for the UK, Europe and the United States".
"But if the British people are determined to do it, so be it," he said.
"However, given the consequences I can't see why it can't be revisited."
He said ideally, the 27 other EU states would agree that a second referendum could take place when the Brexit negotiations were complete.
"If Europe won't agree to postpone it then the vote should be now," he said.
The former special envoy said leaving the EU "can't be good for Northern Ireland" as it will signal a "whole new wave of uncertainty" about the border.
Dr Haass also feels unionists could be the authors of their own misfortune by taking a stance that he believes increases the likelihood of a united Ireland.
"Unionists, who presumably would most oppose Northern Ireland leaving the UK and joining Ireland, favoured Brexit – that to me is an obvious example of how people were not thinking about the first and second order consequences of what they were voting for."
While the former special envoy believes there is no immediate threat to the peace process, he cautioned: "don't rule anything out".
"One of the things I've learned in recent years is to not take anything for granted and not to assume things," he said.
"We've already had the breakdown of the Stormont executive, a new generation of leaders who haven't been tested and a failure to deal with the legacy of the past. I'm not predicting anything bad in Northern Ireland but I don't think the progress that's been made is irreversible."
