The “only option” to avoid any hard border for Northern Ireland would be for the whole of the UK to remain in a customs union with the EU, according to a leaked report.
The document drawn up for the Northern Ireland civil service warns any other solution would lead to border controls with either the Republic Ireland or the rest of the UK.
The report by two legal experts was among 25 official documents related to Brexit which have been leaked by the European Parliament’s GUE/NGL group, which includes Sinn Fein.
It analyses the three options for avoiding a hard border in Ireland which were presented in the Withdrawal Agreement drafted by the UK and EU in December.
The UK’s stated aim was to avoid a hard border in Ireland “through the overall EU-UK relationship” – a trade deal so comprehensive that trade would be frictionless.
Prime Minister Theresa May has also ruled out any solution that would create a customs border between Nothern Ireland and the rest of the UK in the Irish sea.
The leaked report says the “only option that could potentially remove the possibility of a hard border for North-South and East-West trade” would “require the UK as a whole to be part of a customs union with the EU and comply with internal market rules in goods.”
The advice given to Northern Ireland’s top civil servants is revealed as Mrs May comes under growing pressure to rethink her opposition to a customs union with EU after Brexit.
MPs are set to vote on issue after the Lords last week voted for continuing the customs union.
Other options for avoiding any hard border for Northern Ireland are dismissed in the leaked report written for senior civil servants by two Queen’s University Belfast academics.
It warns keeping only Nothern Ireland in the EU customs union would lead to border checks with the rest of the UK.
A third option of maintaining regulatory alignment with the EU outside a customs union “would not remove the need for a hard border.”
The economic consequences of a hard border with either the Republic of Ireland or the rest of the UK are spelt out in another of the leaked documents.
A paper on border controls marked “official sensitive” states: “The trade data shows there is no quick-win in terms of locating border controls; the economy has become integrated into both the Irish and GB markets, so there would be disruption and potential for negative economic impact whether the controls were sited at the land or sea border.”