Boris Johnson has launched an attack on anti-vaxxers spreading “mumbo jumbo” and spouting “complete nonsense” on social media – at a time when significant pressures are being faced by the NHS.

       Contrasting the Covid vaccine rollout to some European countries using “coercion” to jab their populations, the prime minister also stressed the government would maintain its “voluntary approach” to inoculation.

       As the number of NHS hospital trusts on critical alert level increased to 24 and cases of the Omicron variant spread rapidly, Mr Johnson insisted it was now time for the government to “call out” anti-vax campaigners.

       “When you look at what is happening to patients coming into hospital, a large number of them, perhaps 30 to 40 per cent of them, haven’t actually been vaccinated at all,” he stressed.

       “That’s increasingly true of people who go into intensive care – the large majority of them have not been vaccinated at all and the overwhelming majority have not been boosted.”

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       While the vaccine rollout has reached tens of millions of people, an estimated 4.5 million people aged 18 and over in the UK have not yet had a first dose.

       Taking aim at anti-vaxxers, Mr Johnson went on: “I want to say this to the anti-vax campaigners, the people putting this out on social media: they are completely wrong.

       “You haven’t heard me say that before, because I think its very important we have a voluntary approach in this country and we’re going to keep a voluntary approach.

       As Italy announced on Wednesday that Covid vaccinations would be mandatory for people over the age of 50, and Austria unveiled plans last year for mandatory jabs for those over 14, Mr Johnson also insisted the UK would maintain a voluntary approach.

       “We’ve got much higher rates of vaccination in this country thanks to that community-led, voluntary approach – it’s a wonderful thing. Other European countries are going for coercion,” he said.

       “What a tragedy that we’ve got all this pressure on the NHS, all the difficulties that our doctors and nurses are experiencing and we’ve got people out there spouting complete nonsense about vaccination.

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       “They are totally wrong, and I think it’s time that I, the government, call them out on what they’re doing. It’s absolutely wrong, it’s totally counterproductive, and the stuff they’re putting out on social media is complete mumbo jumbo.”

       On a visit to a vaccination centre, the prime minister also described the health and social care levy – which will see a hike in national insurance contributions from April – as “very, very important” to clear the NHS backlog, after reports of a cabinet rift emerged over the plans.