SUPPORT for Brexit in Northern Ireland has plunged since the referendum, a new survey has found.

There was already high support for remaining in the EU, but the uncertainty over the border and the future relationship with the south and Brussels has unsettled previously staunch Leave voters.

In 2016, Northern Ireland voted 56% to remain and 44% to leave, but now a poll, for Queen’s University Belfast, shows support for Brexit has fallen 13 points to 31%. Support for Remain has risen to 69%.

The results came as DUP leader Arlene Foster insisted those talking about the “myths” of border checkpoints were those “committed to unpicking the union”.

But the research showed strong support across the communities for staying in the EU, or at least some form of regulatory alignment with Brussels.

John Garry, principal investigator on the UK in a Changing Europe project and professor of political behaviour at the university, said: “We find Catholics and Protestants most prefer the option that would avoid the need for any new barriers on borders. Either in the Irish Sea or across Ireland. They want the UK as a whole to stay in the customs union and single market.”

Opposition to border checks was higher among Catholic communities. More than half of Catholics (55%) and 70% of those who support Sinn Féin said customs checks were “almost impossible to accept”.

One in five Catholics told the researchers they would find the possible use of cameras at the border “almost impossible to accept” while almost one in 10 Catholics (9%) would support cameras being vandalized.

The researchers said there was strong expectations that protests against either North-South or East-West border checks would “quickly deteriorate into violence”. One middle-aged male Catholic Remain voter told the academics: “The cameras will have to be about 300 feet in the air, and even then … You will get certain people who take the law unto themselves and [will] cut these things down.

“It would have to be the softest hardest border. Military checkpoint is a ‘No No’. Cameras, that would be a ‘No, No' as well…”

“I think the ceasefire would go,” said one Protestant Leave supporter aged 45-59.

“I could see it going the way it was before, with roads being closed off in various places because they can’t properly police it,” said a Protestant voter aged over 60 who supports Remain.

“Protests would start peaceful and then if they don’t get anywhere they would just escalate it,” said a young Catholic Remain voter.

The poll said Catholics were also much more likely to support a united Ireland if there is a "hard" Brexit in which the UK leaves both the customs union and single market.

28% of Catholics would vote for a united Ireland if the UK changed its mind and remained in the EU while 53% of Catholics would vote for a united Ireland if there was a "hard" exit in which the UK left the customs union and single market.

SNP MSP Joan McAlpine said the collapse in support was proof of "just how much of a mess the Tories are making of Brexit". She added: "The Tories took a narrow vote across the whole of the UK – with both Scotland and Northern Ireland voting to Remain – as a mandate not just for Brexit, but for the hardest of hard Brexits.

“But Theresa May can’t even unite her Cabinet around a Brexit plan, never mind uniting the four nations of the UK.

“Almost two years on from the vote, we’re still none the wiser about our trading and customs arrangements with Europe – which are absolutely essential to jobs and prosperity.”

Meanwhile, Foreign Secretary Boris Johnson has insisted South American countries are "desperate" to build trade links with the UK.

Speaking during a visit to Buenos Aires, the Tory said: “In Peru we saw a country that is desperate to do more business with the UK, that is fundamentally open to the world and as a free-market administration under Martin Vizcarra wants to do a big free-trade deal with us.

“We are here in Argentina where relations are improving and you will see tomorrow, when we go to see [President] Mauricio Macri, his determination to take relations with the UK forward.

“There are big opportunities for UK business here. We don’t do nearly enough. There’s a low base, but we are going to build on it very fast. And in Chile it’s the same story - another economy that desperately wants to integrate more closely with the UK.”

He added: “I’m getting a lot of that sort of mood around here. This is something that people are really fired up about.”