Concern is growing within the Garda and the Department of Justice that the Republic will become a transit country, or “staging post”, for illegal immigrants destined for Britain after Brexit.

Garda officers told The Irish Times that when it becomes much more difficult for illegal immigrants to enter Britain, many are likely to come to the Republic with a view to later travelling to Britain illegally.

Senior officers said a much more concerted effort would be needed by Britain and Ireland to prevent illegal immigrants entering any part of the common travel area.

This would involve studying airline advance passenger lists to stop those intending to travel to the Republic illegally from boarding ferries or aircraft.

Garda sources said it was “all but certain” immigration checks would be introduced within the common travel area for the first time. And they said because of the shortage of accommodation in the Republic, centres or camps would need to be built in Ireland if asylum-seeker numbers began to climb.

“Ireland could become a sort of Calais-style camp; people coming here and staying to just wait for their chance to get to Britain,” said one senior officer.

At present, those arriving in the Republic who apply for asylum can then travel by ferry to Britain without passing through immigration checks.

Gardaí believe thousands of asylum seekers who went missing from the Irish immigration system during the past two decades left the country in that way and entered Britain illegally.

You are also looking at stepping up [immigration] controls across the common travel area and policing that as one entity from an immigration perspective

In the 16-year period to the end of 2015, some 16,000 deportation orders were signed in the Republic. Some 40 per cent of the intended deportees are unaccounted for. Most are assumed to have travelled on to Britain.

Gardaí believe that practice will become much more pronounced after Brexit. If so, the number of people claiming asylum in the Republic and living here for a period until they cross into Britain would increase significantly.

Surge in claims

The sources, senior justice figures and Garda officers, cautioned it was difficult to say with certainty how Brexit would affect illegal immigration into the Republic.

However, they pointed out Ireland had witnessed a surge in asylum claims in the relatively recent past.

Before the 1990s there were no asylum claims. However, numbers increased from just nine claims in 1991 to 424 within five years. And over the next five years, as the Republic’s economy took off, the figures surged to more than 11,000 claims annually.

Numbers fell off over the following years, when the entitlement to citizenship through an Irish-born child ceased.

Garda Headquarters believes the Irish and British immigration authorities will need to work closely to combat any rise in illegal immigration into the Republic.

A large emphasis would be put on studying advance passenger lists to ensure those travelling to the Republic illegally are stopped before they boarded flights or ferries.

“You are also looking at stepping up [immigration] controls across the common travel area and policing that as one entity from an immigration perspective,” said one senior justice source.

“That will probably involve having immigration checks for the first time ever as people are leaving Ireland for Britain and vice versa.”