A referendum on British membership of the European Union seems a near certain bet, whether held in 2017 as promised by prime minister David Cameron or a bit later. The political momentum in that direction is simply too strong to be resisted. The outcome is uncertain.

We believe it is manifestly in Ireland’s interest that Britain should remain in the EU. What therefore should Ireland do in the run-up to the referendum? How can Irish interests be preserved and advanced?

The common view of the authors of the book – Britain and Europe: The Endgame – An Irish Perspective – we have jointly edited for the Institute of International and European Affairs is that the long saga of Britain’s troubled relationship with the EU is reaching a critical historical moment when the issue will be resolved one way or the other. This is the closing scene in a relationship where Britain has found it difficult to share external sovereignty in the EU. It is linked to an internal sovereignty question on Scottish independence.

To make sense of the unique relationship between the United Kingdom and Europe, we have developed four scenarios to analyse Britain’s position: 1. Fully in, supporting integration and participating in all policies; 2. Half-in, generally supporting integration but opting out of some policy areas; 3. Half-out, opposing further integration, except where it suited; 4. Fully out, leaving the EU and restoring the pre-1973 position.

The fully-in scenario is not realistic over the next 10 years. The British Labour Party is closest to the half-in position. The Conservatives are closer to the half-out one, though many Conservative MPs and activists would prefer to be fully out.

The British government has been slow to let its European partners know what exactly it wants reformed if it is to argue for Britain to remain in the union. As far as we can see there are seven demands in all: two relating to borders, two dealing with business and trade and three focused on the recovery and preservation of national sovereignty.

Simple proposition

Nor does Cameron wish Britain to participate any further in “ever-closer union among the peoples of Europe” which is at the heart of European integration.

The problem here is that the EU is an open-ended dynamic organisation forever deepening the interdependence of its member states. This is most visible in the euro zone, which has become the de facto core of the union.

We believe it is best for all that Britain remains in the union.

A UK referendum provides an opportunity to turn its problems into the problems of the EU as a whole. It would bring things to a head by securing widespread support for fashioning a form of membership particular – and preferably unique – to Britain: a “bespoke solution” intended to endure and bring the repeated crises in its membership to an end. It would be accepted by the other members that, for the foreseeable future, the UK would be a member of the EU but stay outside the euro zone while remaining inside the single market. The status quo, including UK opt-outs from Schengen, the Fiscal Compact and ever-closer union, would be frozen in time until it chose to join additional common policies.

Many, understandably, are losing patience with Britain; but patience and imagination in negotiation will be required to ensure that the UK remains in the union.

A future EU could have four cores: the single market; the Economic and Monetary Union (including the euro); the Security Union; and a Capital Markets Union as proposed by commission president Jean-Claude Juncker. The Security Union (with British membership) would be based on the common need to protect the EU’s borders from terrorist infiltration, limit welfare tourism and control mass immigration. The UK would be a member of three of the four cores – sufficient for it to be regarded as a core member of the EU as a whole. This would be a multilateral solution to a national problem based on established EU policies and so satisfy honour all round.

British withdrawal from the EU would be a huge shock to the whole European project and to its global influence and reputation.

Deep implications

But the greatest damage of a UK exit would be to the close relationship built up between Dublin and London. Irish-British relations would revert to a damaging bilateralism based more on power relations than interdependence.

If the UK voted to leave the EU and Scotland then subsequently voted to rejoin, resulting in the break-up of the United Kingdom, Northern Ireland would be profoundly unsettled politically and economically.

The role which Ireland can play in the British debate is modest but we should play it with imagination and daring in the interests of the people of our State and of Northern Ireland.

Dáithí O’Ceallaigh was Irish ambassador in London (2001-2007) and director general of the IIEA (2010-2013). He is chairman of the Press Council of Ireland. Paul Gillespie is an Irish Times columnist and an adjunct senior research fellow of the school of politics and international relations at UCD