However, there was confusion on Monday morning over whether he meant jabs would have to be administered by Jan 1 or simply scheduled by the year’s end.

The NHS booking centre for arranging a third jab crashed on Sunday night, moments after Mr Johnson had made a televised address urging all adults in England to get a booster jab.

There were also problems online on Monday morning with ordering lateral flow tests – the Covid tests the Government provides free for people to check if they are infected. Mr Johnson stressed a “ready supply” of lateral flow tests was available.

The issues emerged with the Prime Minister facing the biggest Tory rebellion of his premiership, with up to 75 Conservative MPs considering voting against his “Plan B” restrictions.

The votes in Parliament on Tuesday include widening the face mask mandate and bringing in Covid passports – which show proof of jabs or a negative test – for entry to venues with large crowds.

Speaking during a visit to a vaccination clinic near Paddington, west London, Mr Johnson said: “Sadly, yes, omicron is producing hospitalisations, and sadly at least one patient has been confirmed to have died with omicron.

“So I think the idea that this is somehow a milder version of the virus, I think that’s something we need to set on one side and just recognise the sheer pace at which it accelerates through the population. So the best thing we can do is all get our boosters.”

He said omicron now represents about 40 per cent of new virus cases in London and “tomorrow it’ll be the majority of the cases” in the capital.