Britain will have to accept limited new administrative controls on trade with Northern Ireland in any negotiated Brexit deal, Europe's chief negotiator warned on Wednesday.
Prime Minister Theresa May has insisted that she will not agree to any Brexit that would encroach on British sovereignty, and her Northern Irish allies in parliament have rejected such procedures.
The negotiator said the measures would only be a stop-gap while a new trading relationship is agreed with Britain, and would be minimised if London agrees to join a full customs union under EU rules.
But in the meantime, under the EU vision of a Brexit deal, companies on the British mainland shipping goods to Northern Ireland will fill out "customs declarations online and in advance." "The only visible systematic checks between Northern Ireland and the rest of the UK would involve scanning the barcodes on lorries or containers, which could be done on ferries or in transit ports," he said.
Regulatory checks on industrial goods produced within Northern Ireland for export to the EU could be carried out by "market surveillance regulators" at the factory, rather than at the border.
Finally, existing health checks on animals arriving in Northern Irish port would remain in place but would have to be stepped up to cover 100 per cent of shipments rather than 10 per cent now.
May is due in Brussel next week for an EU summit which the bloc's president Donald Tusk has described as a "moment of truth" for talks on an orderly exit of Britain from the club.
The British sh leader is under pressure to agree an exit deal before March 29 next year, but the Northern Irish party upon which she depends for her majority reportedly threatened Wednesday to vote down the national budget later this month if she gives away too much.
Sources in the Democratic Unionist Party (DUP), which has ten MPs, told the BBC and Sky News they were prepared to break their agreement to support the government in budget matters if May breaches their red lines in Brexit talks.
Getting a budget approved by the House of Commons is traditionally a test of confidence in a government, without which it could fall.
Shortly before the reports emerged, when asked if the government could rely on the DUP, a Downing Street spokesman said: "The confidence and supply agreement that we have with the DUP is a matter of record."
(With inputs from agencies.)