Thousands of travellers entering Ireland from UK will not be included in new passport checks
Thousands of travellers leaving the UK for the Republic of Ireland will not be included in the new passport checks, Britain's Home Office said.
Officials said "alternative arrangements" had been introduced covering the Common Travel Area between the two countries.
Northern Ireland has an open land border with the Republic, meaning travellers from the north using Dublin's ports or airport would not form part of the data.
The number of Northern Ireland residents using Dublin Airport increased by 11pc to more than 570,000 in 2013, according to the Dublin Airport Authority (DAA).
The Home Office has said the exit checks will improve the Government's understanding of who is leaving the UK and create "a much clearer picture of who is staying in the country when they have no right to be here".
They will also help the police and security services track the movements of known criminals and terrorists.
The Home Office said: "The vast majority of passengers leaving the country on scheduled commercial international air, sea and rail routes will go through exit checks.
It added: "Alternative arrangements, separate from exit checks, are being put in place to cover journeys made within the Common Travel Area (journeys between the UK and the Republic of Ireland, the Channel Islands and the Isle of Man)."