People travelling between Britain and the Irish Republic by air or sea will be required to show an identity document under proposals announced yesterday to impose the first formal checks for more than 80 years. The change is to prevent the present free movement between the two countries from being exploited by people-traffickers, organised criminals and smugglers.

Immigration checks are also to be increased along the 224-mile border between the Republic and Northern Ireland, but these will not be fixed controls, so the opportunity will remain for foreigners to gain illegal entry to Britain.

The changes were published yesterday in a Home Office consultation paper. Another consultation paper is to be published in the autumn on whether people travelling between Northern Ireland and the rest of the United Kingdom should be subject to further checks. One proposal is expected to suggest extending the electronic borders scheme, requiring travellers from Northern Ireland to provide their personal details in advance. This would mean residents of one part of the UK being treated differently from others when travelling within the country, something to which Unionists would object.

“We must guard against the risk of any part of our border security becoming a ‘weaker link’,” the paper said. It outlines plans for change to the passport-free zone known as the Common Travel Area, set up in 1925 after Irish independence. It includes travel between Britain and the Channel Islands and the Isle of Man, known as the Crown Dependencies.

In a joint statement, Jacqui Smith, the Home Secretary, and Dermot Ahern, the Irish Justice Minister, said: “It is crucial that our two countries work closely together to ensure our borders are stronger than ever.” They added: “Both governments fully recognise the particular circumstances of Northern Ireland. Both governments reaffirm that they have no plans to introduce fixed controls on either side of the Irish land border.”

The consultation paper said: “We intend to carry out checks on passengers and their documents on sea and air routes arriving and departing from the UK to the Republic of Ireland for border and control purposes. Irish and UK citizens will be required to prove their nationality with a passport or national identity card.”

More than 16 million passengers travelled between the UK and the Irish Republic and the Crown Dependencies in 2006 by air and sea. New laws are also planned to allow searches of vehicles travelling between Britain and the Republic, and airlines and ferry operators face fines for carrying passengers who do not have proper documentation.

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