The Irish government is not underestimating anxiety in Northern Ireland about being taken out of the EU, a senior diplomat has said.
Dan Mulhall, Ireland's ambassador to London, also called for the region to be "front and centre" of imminent negotiations between Downing Street and Brussels on Brexit.
Appearing before a parliamentary committee in Westminster, Mr Mulhall said Northern Ireland was Dublin's "most acute" concern in relation to Britain's decision to leave the bloc.
"The Irish Government does not underestimate the sense of disquiet now felt by many people in Northern Ireland at the prospect of the loss of their connection to the European Union," he said.
Mr Mulhall told the House of Lords Select Committee on the EU that hard work was needed by all to avoid a hard border being erected between Northern Ireland and the rest of the island.
"Any effort to control the free movement of people across the Irish border, or indeed between Britain and Ireland, would be very damaging and I trust that no one would want to contemplate such a step," he told the peers.
"I hope and trust that the particular circumstances that apply in Northern Ireland will be front and centre when it comes to the working out of the UK's future relations with the EU."
The senior diplomat told the parliamentary committee that Brexit will usher in a new era for relations between Britain and Ireland.
"When the UK does leave the EU, Northern Ireland will be in the unique position whereby almost all of its residents are entitled to citizenship of an EU country, Ireland, and we must be alert to the particular circumstances those Irish and EU citizens," he added.