The European Commission is preparing a range of potential responses, including legal action, if Britain decides to use the article 16 clause to suspend aspects of the Northern Ireland protocol.
The contingency planning began in summer but stepped up as hints from London grew that it is preparing to resort to the clause, which allows either side to take limited action unilaterally if the special arrangements are causing “serious economic, societal or environmental difficulties that are liable to persist”.
At a meeting of member state European ministers earlier this week, Germany pressed for the preparation to be done so that the European Union would not be caught off guard were the British government to follow through on the threat to use the article, made by Brexit minister David Frost earlier this month.
On Thursday, Mr Frost escalated the warning with a tweet saying that the protocol was having “a continued negative effect on everyday life and business in Northern Ireland” and demanded an urgent response to changes requested by Britain.
The commission has been preparing to unveil a range of tweaks to ease the implementation of the protocol – which keeps Northern Ireland broadly in line with the EU to avoid the need for a hard border across the island – including a change to EU medicine rules. But the British government has insisted that these do not go far enough.
If London does go ahead with using the clause, one option is for the commission to respond with legal action which could include imposing retaliatory tariffs on British imports.
The circumstances in which article 16 can be used are tightly circumscribed under the withdrawal agreement signed between the EU and UK, and the action that can legally be taken must be limited to addressing the specific areas that are affected.
The withdrawal agreement and trade deal that governs the post-Brexit relationship allow for a range of responses in case of a breach, including infringement proceedings, arbitration mechanisms and retaliatory action on trade in some cases.
The EU insists that negative consequences in Northern Ireland are the result of Brexit, rather than the protocol, which it describes as the solution invented together with the UK government to try to reconcile its departure with the need for an open border with the Republic.
But discomfort with the deal remains among some Northern Irish unionists and parts of the Conservative Party. Prime minister Boris Johnson’s government has called for profound changes to the arrangements in its “command paper” on the issue, including a challenge to the role of the European Court of Justice.
The EU views this as a bid to reopen negotiations on the deal, which it has ruled out, calling for the agreement to now be implemented so that businesses can have certainty.
At an EU-UK committee on the implementation of the protocol on Friday, British officials called for “significant changes to the protocol” and said it was “now urgent to make progress on revised arrangements”, a government statement said.
It would continue to operate the protocol “on its current basis while discussions continue”, the statement added.