The European Union has demanded access to AstraZeneca vaccines manufactured in UK plants as the bloc's row with the pharmaceutical giant over a shortage of doses intensified.
European health commissioner Stella Kyriakides told the firm on Wednesday it is contractually obliged to send jabs produced in Oxford and Keele to EU member states.
AstraZeneca chief executive Pascal Soriot argued supply chain "teething issues" were fixed in the UK ahead of the bloc because Britain signed a contract three months earlier.
But Ms Kyriakides said: "We reject the logic of first come first served. That may work at the neighbourhood butchers but not in contracts."
— Stella Kyriakides (@SKyriakidesEU) January 27, 2021
She denied the bloc would impose an export ban on vaccines leaving the EU but said the contract signed with AstraZeneca, which worked with Oxford University on its vaccine, contains two factories in the UK.
"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," she added.
"We expect the doses that are in an advance purchase agreement to be delivered to the European Union."
There were concerns that the UK could face supply issues for the Belgium-manufactured Pfizer jab if the EU imposed export controls, as previously suggested.
But Ms Kyriakides said: "Let me be absolutely clear, the European Union is not imposing an export ban on vaccines or restricting the export of vaccines to third countries.
"What we have proposed as a commission is an export transparency mechanism. What it will do is bring clarity on the production capacity of manufacturers."
In an interview with Italy's La Repubblica newspaper, Mr Soriot said "we are basically two months behind where we want to be" in supplies due to manufacturing issues in Europe, citing problems in a Belgian plant.
He said there had been "teething issues" in the UK supply chain as well but that the deal with Britain was signed three months ahead of the EU's.
"So with the UK we have had an extra three months to fix all the glitches we experienced," he said.
He rejected the suggestion the firm was selling to the highest bidder "because we make no profit everywhere" under the agreement signed with Oxford University.
Prime Minister Boris Johnson said on Tuesday that he had "total confidence" in the UK's supply of jabs.