Open borders between Ireland and the UK are being exploited by illegal immigrants, according to a British intelligence report published today.
The UK's National Criminal Intelligence Service (NCIS) said the situation was a result of the common travel area agreement, which allows unhindered voyage between the Republic and the UK.
Its annual UK threat assessment said: "Efforts have been made by both governments to address this situation and there have been a number of successful detections and interdictions of illegal migrants."
"Illegal migration in both directions between the Republic of Ireland and the UK, exploiting the Common Travel Area agreement, is a cause of concern."
Last month Britain's Home Office minister said there was "no expectation" that people who commute into Northern Ireland from the Republic would be required to carry ID or passports if the British government decided to introduce madatory ID cards.
MP Andrew Mackinlay said this arrangement Ireland could put "a coach and horses" through the British government's plans.