Belfast Border Officer jobs will only be available to applicants with British passports
Sinn Féin has hit out at the requirement, claiming it is the first sign of a hard border.
Border Force officers looking to apply for jobs based in Belfast will be required to hold full British passports ahead of Brexit.
Currently advertised through the British Home Office, the 16 Border Force Office roles at Belfast International Airport and five Assistant Officer jobs in Belfast will require applicants to be UK citizens, while a "full and valid British passport" must be presented at any interviews.
The requirements, which are laid out in the candidate information packs, state clearly that "These are reserved posts and are only open to UK nationals... You should normally have been resident in the UK for the last five years."
However, "due to the sensitive nature of the work, [which requires] special allegiance to the Crown", Irish passport holders living in Northern Ireland are ineligible for the positions.
This dual-citizenship is a right afforded to anyone born in Northern Ireland, and as a result, it has been cited as discriminatory.
Rejecting what he saw as "naked discrimination of a public sector position" and a "statement of intent" to introduce a hard border, Sinn Féin's Newry-Armagh MLA Conor Murphy said: "With this British Border Force recruitment drive, the British government are clearly planning to impose their hard Brexit border across the island of Ireland.
"It shows that the Tories see a hard border as the predetermined outcome of the Brexit negotiations despite the fact they have already agreed to an option to avoid it.
"There can be no Tory-DUP Brexit border across Ireland. This is a deeply damaging, disruptive and dangerous position, rejected overwhelmingly by the people of this island.
"It also points to the Tory-DUP pact's growing disregard for the Good Friday Agreement, which allows citizens to determine their own identity free from discrimination.
"Not only are they ignoring the democratic expressions of Irish citizens, they're also actively excluding them by reserving these posts solely for citizens with British passports."