Long-standing freedom of travel and residency arrangements between Ireland and the UK are “written in sand” and may need a separate Anglo-Irish treaty after Brexit, a group of academic lawyers has warned.

The terms of the Common Travel Area – in existence for almost a century – are “much more limited than is often believed,” new research to be presented today to a joint human rights committee set up under the 1998 Belfast Agreement states.

An 85-page report by four UK-based law academics recommends the Irish and UK governments should agree “a new intergovernmental Common Travel Area treaty” to formalise common immigration rules, travel and residency rights and other social, policing and security arrangements.

The report warns the Common Travel Area has been overplayed as a solution to avoid a hard Irish border.

Protections

The Common Travel Area, which covers protections for Irish and British people to work and travel in each other’s countries and for access to healthcare, education and social welfare payments, would benefit from “greater legal certainty to continue their “smooth operations” after Brexit, the report says.

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The research has been prepared for the Joint Committee of the Irish Human Rights and Equality Commission and the Northern Ireland Human Rights Commission.

The Common Travel Area, the report finds, is not underpinned by a single legal agreement but “a hotchpotch of laws”.

The report is written by law academics Sylvia de Mars of Newcastle University, Colin Murray of Newcastle University, Aoife O’Donoghue of Durham University and Ben Warwick of the University of Birmingham.

Mrs May last night described negotiations over Brexit as “immensely difficult”, with significant issues in the withdrawal agreement still to be resolved. Speaking at the Lord Mayor’s banquet at the Mansion House in London, the prime minister suggested that speculation about an imminent breakthrough in the talks was premature.

‘Bucket of salt’

Today’s British cabinet meeting will not discuss a Brexit deal, contrary to comments attributed to EU chief negotiator Michel Barnier yesterday suggesting that the outline of a deal was ready for British ministers to consider. Ms May’s official spokesman said such speculation should be taken with “a bucket of salt”.

The critical outstanding issue remains the so-called backstop and how the invisible border would be maintained, should no better solution be found in a wider EU-UK trade deal agreed in future.

Senior Government figures said that the backstop could be reviewed regularly but suggested a British proposal for a review every few months was too frequent. Negotiators are trying to agree a deal on conditions that Brussels would apply to the whole of the UK remaining in the customs union for a temporary period in order to avoid a hard border and how the backstop would end so as to appease hard Brexiteers who fear remaining under EU rules indefinitely.