The successful development of "electronic" borders and the necessary protection of the Common Travel Area between the UK and the Republic will require the virtual integration of British and Irish immigration controls.
That is the verdict of some senior Northern politicians tracking current British legislation to effect tighter "UK" border controls and Taoiseach Bertie Ahern's initial comments on the development of "an Irish border system" likely to be "similar in some ways to the British system".
At the same time Ulster Unionist peer Lord Kilclooney (former MP John Taylor) has warned against a possibly anomalous situation which could see British citizens in Northern Ireland required to provide proof of identity when travelling to other parts of the United Kingdom.
"That would be political dynamite, unionists would be outraged," he said yesterday when asked about the possibility that the new border controls might apply as between "Britain" and "Ireland" while apparently having no significance for "the land border" between Northern Ireland and the Republic.
Lord Kilclooney was reacting to Wednesday's Irish Times report signalling the possible end of the Common Travel Area (CTA) and a future requirement that Irish citizens entering Britain produce a passport. In the Dáil on Wednesday Mr Ahern said "further border controls" would be required between North and South by authorities targeting illegal immigration.
However, he also said: "There are no plans to introduce any controls on the land border between North and South."
Lord Kilclooney and other peers are not advocating the land border become the "first line of defence" for the British state against terrorists and other threats - but rather for a uniformity of approach on an islands-wide basis that would require a comprehensive agreement between the British and Irish governments.
Lord Kilclooney said: "The Common Travel Area between the United Kingdom and the Republic of Ireland requires common controls, whether entry is in Dover or Cork."
In the House of Lords earlier this month he also warned that failure to enforce common controls throughout what he calls "the British isles" would render the Labour government's current UK Borders Bill "null and void".
Lord Kilclooney asked: "Will there be immigration officers on the land boundary between the UK and the Republic? If not, will the Republic of Ireland apply the same entry requirements as immigration officers will require when people enter Great Britain?"
He then argued: "If not - people will enter the Republic of Ireland - as they do now - and move freely across the land border into the UK. Therefore the impact of this bill will be null and void."
Recently ennobled Lord Paul Bew also joined the debate yesterday, suggesting that ID cards - British and Irish, with security, customs, immigration and other authorities accessing the relevant national databases and sharing information - might be the best way to resolve political sensitivities surrounding the position of nationalists in Northern Ireland and the large Irish community in Britain. Under the terms of the Belfast Agreement people in Northern Ireland can define themselves as British or Irish or both.
Meanwhile, Northern Ireland security minister Paul Goggins has confirmed that illegal immigrants do cross the land border from the Republic into Northern Ireland. In a letter to Lord Kilclooney, Mr Goggins said the Borders and Immigration Agency (BIA) assessment is that only a small number of these people remain in Northern Ireland, with most travelling on to Britain. Mr Goggins quotes the British government's Border & Visa Strategy: Securing the UK Border, published in March, identifying that the Common Travel Area "poses an immigration risk".
The agency estimates that the number of illegal immigrants travelling in the opposite direction (from the UK to Ireland) is about the same.
The immigration agency, he says, has committed to the monitoring of all air and sea movements across CTA borders via e-Borders by 2011; to share more data with its Irish counterparts and increase the number of joint operations; deepen coverage of CTA borders by closer collaboration between UK border agencies; explore the potential for additional checks on passengers travelling within the CTA; and review the rules governing CTA border activity, based on the principle that CTA nationals are not subject to immigration control on the internal borders.