Former British attorney general, Dominic Grieve, said the chances of an Irish border poll will "go up" putting the status of the North in "jeopardy" if Britain crashes out of the EU without a deal.
Speaking in Dublin the Conservative MP said: "A crash-out Brexit makes a political crisis in respect of Northern Ireland's future status more likely... clearly the chances of a border poll go up for a whole variety of reasons.
"The status of Northern Ireland under the Good Friday Agreement remaining in the UK has worked because in truth there's been a clear majority of the population who have been very comfortable with the arrangements that the Good Friday Agreement has delivered and that includes sections of the nationalist community as much as the unionist and that will be thrown into jeopardy by a no-deal Brexit.
"Indeed Brexit itself is probably likely to put it under strain even if it is done in a controlled fashion."
Mr Grieve told reporters ahead of a speech in Dublin that potentially bringing about Irish unification through the mechanism of Brexit has always struck him as being "a very bad idea".
Asked whether a no-deal Brexit raises the risk of violence in the North, Mr Grieve said: "It worries me because I think I know Northern Ireland well enough to know that acceptance of change, even if you have a minority status, doesn't always follow. After all the whole history of the Troubles was of a series of perfectly clear grievances held by sections of the Northern Ireland community which meant that they wouldn't accept ordinary democratic processes in Northern Ireland because they felt that as a result their status and way of life was under threat and they were also discriminated against and there were enough of them to create violence.
"And in the exactly same way, in my view, the same exists within the loyalist community."
The MP is among a group of "Tory rebels" opposed to a no-deal Brexit.
He told RTÉ earlier he believes that if the British government tries to push through a policy against the wishes of the House of Commons, it is likely to fall on the motion of no-confidence.
Mr Grieve said that when the House of Commons returns in September, Britain faces a "period of major political crisis" with just eight weeks before it is set to leave the EU.
He said while he can not be certain Britain will not crash out, he thinks it is unlikely.
Mr Grieve repeated his belief that a second referendum is the only way out of the current situation.