Liz Truss has been urged to show she is prepared to follow through on her threat to trigger Article 16 in Brexit talks.
Think tank boss Mark Littlewood said it would “focus minds” in the European Union if they thought the UK would take the nuclear option.
Mr Littlewood, director general of the Institute for Economic Affairs free market think tank, said: “I think if we can’t find a workable solution then what the Foreign Secretary has intimated and I agree with is that we will have to trigger Article 16.
“It seems to me pretty unambiguous that this is causing damage socially and economically to the people of Northern Ireland.
“So as a final resort, I think we should be unapologetic about triggering Article 16. It seems to me all of the necessary evidence is there that would make that wholly justifiable.
“And perhaps if the European Union think that we might actually trigger it that will focus some minds and we can find an easier solution.
“I think we can get there and I think we will get there. I think the only question is whether this is done by sensible discussion and debate, or whether we have to do it unilaterally by triggering Article 16.”