DUP leader Arlene Foster has claimed chief Brexit negotiator Michel Barnier does not understand unionist culture in Northern Ireland.
Mr Barnier is in the Irish border towns of Dundalk and Newry on Monday before visiting Londonderry on Tuesday.
Mrs Foster said: “I don’t think he does understand the wider unionist culture of Northern Ireland.
“He’s hearing a very strong message from the Republic of Ireland’s government, he’s hearing it from Sinn Fein.
“We have tried to get him to understand the unionist position for the people of Northern Ireland, but he hasn’t really responded to that, and I’m disappointed about that.
“I’m also disappointed that he will hear anti-Brexit voices tomorrow, he won’t hear any pro-Brexit voices tomorrow because he is being taken around by Sinn Fein MPs.”
The chairman of the European Research Group of Tory Eurosceptics, Jacob Rees-Mogg, said the UK should call the EU’s bluff over the Irish border.
Mr Rees-Mogg told LBC radio: “I would call their bluff. I would say, ‘OK, we’re not putting up a border, are you?’
“That would leave the challenge to the Irish Government to decide whether it wished to put up a Trump-like wall between the Republic of Ireland and Northern Ireland. I doubt they want to do that.”
He added: “If we leave without a deal and impose the common external tariff against the Republic of Ireland, that’s extremely damaging to the Irish economy. The Irish Government ought to understand the risk it is taking, and the EU likewise.”