Former Chancellor George Osborne has said Northern Ireland is now on its way out of the Union as a result of Brexit and that most people outside the region just don't care.
And the former Tory MP, who is editor-in-chief of the London Evening Standard, laid the blame squarely at the door of the DUP because of its backing for withdrawal from Europe.
But the party's Sir Jeffrey Donaldson hit back last night, saying a clear majority of people here wanted to remain in the UK.
Writing in his newspaper, Mr Osborne stated that "by unleashing English nationalism" Brexit had made the Union "the central political issue of the coming decade".
He recalled his "worst evening" in Downing Street: "Sitting in the small wood-panelled dining room in Number 11 with David Cameron, eating a tepid curry, waiting for the results of the Scottish referendum.
"We thought: are we the people who have lost Scotland? History allows for no recovery from a disaster like that.
"Ask Lord North, the Prime Minister condemned for all-time for the loss of America.
"The mistake he made - and with Irish calls for Home Rule a century later - had been to assume that doing nothing was an option.
"Our referendum was a proactive plan to keep the United Kingdom together, and it looked like it had put Scottish nationalism back in its box for a generation.
"Not any more. By unleashing English nationalism, Brexit has made the future of the UK the central political issue of the coming decade."
He added: "Northern Ireland is already heading for the exit door.
"By remaining in the EU single market it is for all economic intents and purposes now slowly becoming part of a united Ireland.
"Its prosperity now depends on its relationship with Dublin (and Brussels), not London. The politics will follow."
The Tory grandee added: "Northern Irish unionists always feared the mainland was not sufficiently committed to their cause.
"Now their short-sighted support for Brexit (and unbelievably stupid decision to torpedo Theresa May's deal that avoided separate Irish arrangements) has made those fears a reality.
"It pains me to report that most here and abroad will not care."
In response to Mr Osborne's comments, Sir Jeffrey said he was entitled to his opinion, but he had ignored recent polling that suggested the majority of people here wanted to remain part of the UK.
"We don't believe Brexit is going to change that significantly," the Lagan Valley MP said.
"There are issues and problems with the NI Protocol but they would have been much worse if we had adopted Theresa May's backstop."
Sir Jeffrey said the backstop would have permanently separated Northern Ireland from the rest of the UK.
"The measures that were proposed for Great Britain were merely temporary and for a short period," he said.
"We would have been left inside both the EU customs union and the EU single market, and whatever the difficulties with the NI Protocol, it certainly didn't go as far as the backstop in leaving Northern Ireland out on a limb.
"We won't accept a rewriting of the history by George Osborne or anyone else. I think most people will see through this."
The veteran unionist said Northern Ireland's place within the UK was "not dependent on what people think in other parts of the UK".
"Under the Good Friday Agreement it is solely dependent on the democratic wishes of the people of Northern Ireland alone," he said.
He also disagreed with Mr Osborne's assessment that the majority would not care if Northern Ireland left the Union.
"I believe there are many unionists across the whole of the UK who believe passionately in maintaining the Union, and if George has abandoned that cause that doesn't apply to many across all the countries in the Union," he claimed.