Sir Keir Starmer needs to stop people-smugglers using Northern Ireland as a backdoor route into Britain, senior Unionists have warned.
The UK-Ireland "open border" could increasingly see abuse by migrants - especially if Starmer's "one in, one out" deal with Emmanuel Macron reduces Channel crossings.
The "Irish route" refers to a smuggling route which sees migrants fly from mainland Europe to Dublin, and then cross the land border unchecked into Northern Ireland to claim asylum in the UK.
The "loophole" comes thanks to the Common Travel Area - which allows free movement for British and Irish citizens, and predates both countries' EU memberships.
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|The PM has been urged to stop people-smugglers using Northern Ireland as a backdoor route into Britain
MP for North Antrim and TUV leader, Jim Allister, has vowed that "the people of Northern Ireland deserve the same border security and immigration enforcement as anywhere else in the United Kingdom" as a result.
He said: "If the Prime Minister is serious about securing the UK's borders, then it's time to stop pretending that our only border threat comes from the sea.
"Failure to act continues to foster illegal settlement, demographic manipulation, and strain on public services - particularly in areas like Ballymena, where the impact is plain to see."
Last month saw over a week of unrest in towns across Northern Ireland, after rioting first broke out in Ballymena following an alleged sexual assault in the town.
PA | Last month saw over a week of violence in towns across Northern Ireland, after rioting first broke out in Ballymena after a peaceful protest over an alleged sexual assault in the town
Two teenage boys appeared in court accused of sexually assaulting a teenage girl, speaking through a Romanian interpreter to confirm only their names and ages.
As of the end of June, 41 people had been arrested in connection with the "recent racially-motivated disorder".
The growing fury over immigration in Northern Ireland was highlighted last week when a bonfire was burnt with an effigy of 12 migrants in a small boat carrying the Irish tricolour on top.
Strapped to the side of the pyre, which came ahead of the annual July 12 Unionist celebrations, was a sign reading "stop the boats" and another banned reading "veterans before refugees" alongside an image of two guns.
LATEST ON THE UK'S MIGRANT CRISIS:
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|PICTURED: A bonfire is burnt with an effigy of 12 migrants in a small boat carrying the Irish tricolour on top
And with fears skyrocketing over the loophole, DUP peer Lord Dodds told The Telegraph: "We will be telling the Government to closely monitor the flow of people and do what is necessary to protect and defend the entire border of the UK."
While no immigration checks are made on the Irish land border itself, intelligence-led operations are carried out on travel routes further from it in order to stop abuse.
However for many, this is not enough.
Robin Swann, UUP MP for South Antrim, said: "Whatever steps the Government takes, they must also ensure that there isn’t an unchecked illegal route through the Republic of Ireland.
"If the Gardai can mount checks on public transport travelling from Northern Ireland to the Republic, UK authorities should be doing likewise."
The Unionist warnings come just weeks after a major crackdown on people-smuggling networks exploiting the Common Travel Area between the UK and Ireland.
The crackdown focused on ports and airports across Northern Ireland, northwest England and Wales, with Home Office Immigration Enforcement teams leading the effort.
Both illegal migrants and suspected people-smugglers were among those detained in what the Home Office described as a "Northern Ireland people-smuggler crackdown".
Officers seized £17,000 of suspected criminal assets during the operation, the department said.
GB News has approached the Home Office for comment.