A senior EU official has suggested coronavirus vaccines produced in the UK should be shared with the bloc, as its supply comes under pressure.
Brussels's health commissioner Stella Kyriakides said given AstraZeneca is blaming production problems at factories in Europe on the shortfall in jabs delivered, the pharmaceutical giant's plants in Britain should be used instead.
"We reject the logic of 'first come, first served' - that may work at the neighbourhood butchers but not in contracts," she said on Wednesday.
"There is no hierarchy of the factories. You are aware in the contracts there are four factories listed but it does not differentiate between the UK and Europe.
"The UK factories are part of our advance purchase agreements and that is why they have to deliver."
Her comments come amid an escalating public row between the EU and AstraZeneca, with discord still evident after a meeting between the two sides yesterday.
After the meeting, Ms Kyriakides said her team "regret the continued lack of clarity on the delivery schedule" and added they asked AstraZeneca for a "clear plan" to ensure "the fast delivery of the quantity of vaccines that we reserved".
Meanwhile, a spokesman for AstraZeneca said it had discussed the "complexities of scaling up production" of the vaccine, and will "continue our efforts to bring this vaccine to millions of Europeans at no profit during the pandemic".
The row blew up after AstraZeneca announced it would have to cut the amount of jabs delivered before the end of March from 80 million to 31 million.
Brussels believes it will get even less than that - just one quarter of the doses that member states were supposed to get during the first three months of 2021 - and has accused AstraZeneca of a breach of contract.
But the UK government is insisting that Britain's vaccine orders should not be affected by the EU's troubles.
"I think we need to make sure that the vaccine supply that has been bought and paid for, procured for those in the UK, is delivered," Cabinet Office minister Michael Gove told LBC.
He added: "Of course, we're always going to work with our friends and neighbours, we have to make sure that we can do everything we can to help them.
"But our priority has to be making sure that the people in our country who are vulnerable and who we have targeted for vaccination, receive those jobs in those arms."
While the finger pointing on the continent continued, Prime Minister Boris Johnson avoided being drawn on any potential impact of the dispute on UK vaccine supplies during a Downing Street news conference.
Asked if he would impose an export ban to stop jabs leaving Britain, he said he was "very confident in our contracts" for the vaccine, which was developed in the UK at Oxford University.
AstraZeneca chief executive Pascal Soriot said the supply chain in Europe still has "teething issues" - something which had been ironed out in the UK because the contracts were agreed three months earlier.
He told German newspaper Die Welt: "The reason why we said [it's a best effort] is because Europe at the time wanted to be supplied more or less at the same time as the UK, even though the contract was signed three months later."
Over three nights Sky News will host a series of special programmes examining the UK's response to the pandemic.
Watch COVID Crisis: Learning the Lessons at 8pm on 9, 10 and 11 February