The European Commission said the revised “vaccine transparency mechanism” would also target countries that made coronavirus vaccines but did not export them to the bloc.
Brussels is furious with AstraZeneca after the company announced a series of supply shortages, and companies that fail to meet their contractual obligations are also targeted by the new rules.
Its trade and health commissioner denied the ban was a punishment for Britain’s vaccination success, which has stung more than half of its adult population compared to just 12% in the EU.
But when asked which country could be hit hardest, Valdis Dombrovskis, the trade commissioner, gave the UK example.
He said the EU exported around 10.9 million vaccines, mostly from the Belgian Pfizer plant, to the UK, but Britain had not sent a package to the bloc.
The commissioners said any decision to ban exports would be based on reciprocity, on whether a destination restricts exports to the EU and on proportionality – whether conditions in the destination country are better or worse than those of the EU.
The commission has previously threatened to use the mechanism to block the export of millions of AstraZeneca vaccines from the company’s Halix plant in Leiden, the Netherlands.
Mr Dombrovskis did not deny that Pfizer’s exports to Britain could be blocked. He said decisions would be made “on a case-by-case basis”.