The European Union on Friday sought to restrict exports of Covid-19 vaccines to Northern Ireland by overriding a part of the post-Brexit deal with Britain, a steep escalation of the bloc's battle to secure vaccine supplies.
Northern Ireland First Minister Arlene Foster described the move as "an incredible act of hostility".
The EU has turned to Article 16 of the Northern Irish Protocol to launch its foray, a clause which allows Britain or the EU to take unilateral action if there is an unexpected negative effect arising from the agreement.
"By triggering Article 16 in this manner, the European Union has once again shown it is prepared to use Northern Ireland when it suits their interests but in the most despicable manner – over the provision of a vaccine which is designed to save lives," said Ms Foster.
The article was devised as a last resort to alleviate serious disruption to trade in Northern Ireland after Brexit.
A spokesman for the British government said senior cabinet minister Michael Gove had expressed to the EU "concern over a lack of notification", and said it would be "carefully considering next steps".
The EU move is designed to prevent the open border between EU-member Ireland and Northern Ireland from acting as a backdoor for vaccine supplies into the United Kingdom.
It was not immediately clear if the move to invoke the article, set out in a document published on Friday, would come into effect immediately. A link to the document was no longer working at 20.50 GMT.
The EU, whose member states are far behind Israel, Britain and the United States in rolling out vaccines, is scrambling to get supplies just as the West's biggest drugmakers slow deliveries to the bloc due to production problems.
By contrast, the United Kingdom has secured 367 million doses of the seven most promising vaccines, including 100 million doses of the AstraZeneca vaccine which was developed by Oxford University.
Among those procured by Britain include a vaccine developed by Novavax, which on Thursday said it proved 89 per cent effective in a UK trial, and Johnson & Johnson, which on Friday said its shot was between 72 per cent to 66 per cent effective.
Kate Bingham, the former head of Britain's vaccine taskforce, said the country had been able to secure supplies by supporting pharmaceutical companies, setting up clinical trials quickly and helping firms procure equipment to increase manufacturing.
She declined to comment on the detail of the contract with AstraZeneca but said the United Kingdom had benefited from early work to be ready to make vaccines.
EU says move justified by desire to avoid societal unrest
The British-Swedish drugmaker AstraZeneca has been caught in the crosshairs after it said last week it would fall short of delivering promised vaccines to the EU by March because of production problems in Belgium.
That has angered Brussels which has demanded to know why it cannot divert supplies from its British sites which have been producing millions of shots for British citizens.
The European Commission has agreed a plan to control exports of vaccines from the bloc, including to Britain, arguing it needed to do so to ensure its own supplies.
The Commission said its move to invoke Article 16 was justified to "avert serious societal difficulties" in EU states due to a lack of vaccine supply, the document published on Friday said.
Britain has its own domestic supply chain in place for AstraZeneca's shot, including rolling it out in Northern Ireland, but it imports Pfizer's vaccine from a factory in Belgium.
