The PM’s comments came after AstraZeneca Covid-19 vaccine was ruled to be “safe and effective” – with its benefits outweighing any risks - by the European Medicines Agency (EMA).

However, the European regulator said it “cannot rule out definitively” a link between “a small number of cases of rare and unusual but very serious blood clotting disorders” and the vaccine, though investigations were ongoing. Following the ruling, Italy, France and other EU nations announced it will resume giving the jab.

It comes after it emerged five men in the UK have suffered an “extremely rare” blood clot problem after having the AstraZeneca coronavirus vaccine, though no causal link with the jab has been established.

More than 25 million people in the UK have now received a first dose of a coronavirus vaccine, but the NHS has warned of a month-long “significant reduction” in weekly supply of the jabs.

An AstraZeneca spokeswoman said: “Our UK domestic supply chain is not experiencing any disruption and there is no impact on our delivery schedule.”