Theresa May's model of Brexit will hike support for a united Ireland, a devastating study suggests today.
The research claims voters believe leaving the EU could make the break-up of the United Kingdom more likely.
It comes after months of fears that Brexit will lead to a return of customs checks on the border between Northern Ireland and the Republic.
Academics at Queen’s University Belfast found there is "substantial and intense opposition" to any north-south border checks - and to any checks between Northern Ireland and the rest of the UK.
And there are "strong expectations" that any protests against such checks would "quickly deteriorate into violence", the experts said.
It comes despite Tory Brexiteer Michael Gove claiming today that Brexit will give a "boost" to those trying to keep the Union together.
The key finding was that 28% of Catholics would vote for a united Ireland if the UK changed its mind and remained in the EU.
But this figure soared to 53% of Catholics if the UK leaves the EU's customs union and single market - which is Theresa May's plan.
Meanwhile support for staying in the EU has risen overall across Northern Ireland, the academics found.
Some 69% said they would vote Remain now compared to 56% in the EU referendum of 2016.
And 61% of people in Northern Ireland are in favour of staying in both the customs union and single market, the study said.
One in five Catholics found the possible use of cameras at the border ‘almost impossible to accept’ and almost one in 10 Catholics (9%) would support cameras being vandalised.
Cabinet ministers still haven't agreed on a customs policy after 2020 amid a row between the government and Tory Hard Brexiteers.
Brexiteers oppose a 'customs partnership' which would see Britain collect tariffs on the EU's behalf - due to its close ties to Brussels.
They want a 'max fac' plan, with some electronic border checks, that Brexit Secretary David Davis will probe on a trip to Northern Ireland today.
But this 'max fac' plan, short for maximum facilitation, faces being rejected or vandalised, today's study suggests.
One middle-aged male Catholic Remain voter told the study: "The cameras will have to be about 300 feet in the air".
Even then, the voter said, "you will get certain people take the law unto themselves and [will] cut these things down."
Theresa May previously clashed with Tory Brexiteer Jacob Rees-Mogg, reportedly warning she would not risk breaking up the Union.
John Garry, Professor of Political Behaviour at Queen’s University Belfast, 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."
The study, for think tank UK in a Changing Europe, polled 1,012 people in Northern Ireland through Ipsos MORI between February 9 and March 12.
The results were then added to by a day-long in-depth forum with 48 people selected to be from a range of genders, ages, social classes, religions and Leave and Remain votes.