EU to publish to publish first Brexit treaty, saying Northern Ireland should stay in EU customs union

The European Union is due to lay out its first complete Brexit strategy draft later this week. The draft is likely to prompt debate over the question of the Irish border.

In a document to be finalised on Wednesday, the European Commission will say that as a last resort to avoid a hard border, Northern Ireland would remain in the EU customs union and aligned to European single market rules.

Downing Street has dismissed any prospect of a return to a hard border.

But the DUP has said if the Irish Sea became a trade border it would withdraw its support for the UK government.

One senior EU diplomat said the text would reflect that unless there are mutually-agreed alternatives: “Northern Ireland is to stay in a de-facto customs union with the EU combined with alignment on trade in goods.”

Another one of the party's senior members, Sir Jeffrey Donaldson, tweeted: "This fundamentally breaches the understanding reached in December and would undermine the constitutional status of NI in the Belfast Agreement.

"If the EU or Dublin believes the UK government will be signing up to a border in the Irish Sea, they are deluded. Taoiseach (the Irish prime minister) knows that."

British and European negotiators papered over their divisions on Ireland with an agreement on phase one of Brexit talks last December. The agreement, which contained a 15-paper joint report, is now being turned into a formal legal treaty by EU lawyers, leaving no room for ambiguity about the status of the Irish border. 

Now, the British government will be presented with a 200-page Brexit treaty that consisted more than 160 legal articles.

The European commission’s leadership is expected to sign off the draft on Wednesday, before handing it to national diplomats of the EU’s remaining 27 member states who aim to revise the draft by the end of March.

Michel Barnier, the EU’s chief negotiator, wants to agree a final version with the UK by October 2018.

According to reports by Irish broadcaster RTE, the text will say that Northern Ireland may be considered part of European Union customs territory after Brexit, alluding to a single "regulatory space" on the island of Ireland with no internal barriers.