At least one person in the UK has died with the Omicron variant of Covid-19, Boris Johnson has said, as he refused to rule out tighter restrictions ahead of Christmas.

Speaking during a visit to a vaccination clinic near Paddington in west London, the Prime Minister 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.”

It came after Health Secretary Sajid Javid said the Government will “throw everything at” the booster programme to tackle Omicron, which is spreading fast across the UK.

Mr Johnson repeatedly declined to rule out further coronavirus restrictions ahead of Christmas as he said the goal is to offer a booster to every adult by the end of the year.

There has been confusion over whether people will be guaranteed a jab by December 31, with NHS England saying everyone will have been offered the chance to book a booster.

On Sunday, the Prime Minister said people would be able to “get” their jab by that date.

Speaking to broadcasters during his visit on Monday, the Prime Minister said: “Throughout the pandemic I’ve been at great pains to stress to the public that we have to watch where the pandemic is going and we take whatever steps are necessary to protect public health.

“We think the steps that we are taking – so Plan B, combined with a hugely ambitious acceleration of the booster campaign, bringing it forward by a month so we offer a booster to every adult by the end of the year – we think that’s the right approach.

“We now want to hit warp speed and we’ll have to attain a pace and a number of daily booster doses that will exceed anything that we’ve done before.

“But I’ve got no doubt at all that we have the people, we have the enthusiasm, we have the fundamental optimism about what we can do, which we’ve learned from the experience of the last 18 months. And I know that people are going to rise to this.”

In England a booster is available to everyone aged 18 or over from this week as long as the second dose was at least three months ago.

Over-30s can already book a booster online and, from Wednesday, this will be extended to over-18s.

The Prime Minister’s official spokesman later said that if those eligible booked in time, they had the offer that they could receive the jab – not just book an appointment for later – by the end of December.

He said: “We absolutely aim to meet this commitment. It is vitally important. I think we can see the strong response from the public.”

England’s chief medical officer Professor Chris Whitty acknowledged the increased pressure on the NHS, saying it is “once again facing a rising challenge”, and tweeting a “profound thank you” to health staff for their efforts.

Mr Johnson said MPs thinking of rebelling against Plan B measures needed to recognise there was “no room for complacency” in dealing with Omicron.

Asked about support among his backbenchers ahead of Tuesday’s vote, the Prime Minister told broadcasters: “I think that what everybody needs to recognise is a couple of things – that Omicron is a very serious risk to public health, and that it’s spreading very fast, and I think there’s no room for complacency.

“But we have the vaccines, our position remains incomparably better than it was last year. And I hope that people will also understand – colleagues in Westminster, around the country – will also see that the measures we’re putting in place are balanced and proportionate.”

Responding to the fact the Government website said on Monday “there are no more home tests available” when people tried to order lateral flow kits, the Prime Minister said there was a “ready supply” of tests.

He said: “They can get those tests, we do have a ready supply of lateral flow tests.

“If you can’t get one online for any reason, then there are ample supplies in the shops. But what I think, if I may say so, what that also shows is that people are doing the sensible thing, and getting tests as well.”

The UK Health Security Agency said earlier that “due to exceptionally high demand, ordering lateral flow tests on gov.uk has been temporarily suspended to fulfil existing orders”.

It added: “Everyone who needs a lateral flow test can collect test kits – either at their local pharmacy, some community sites and some schools and colleges.”

Earlier, Mr Javid said there were 10 people in hospital in England with Omicron, but warned that cases, hospital admissions and deaths will rise.

The UK Health Security Agency said the 10 are spread around the country and their ages range between 18 and 85.

The majority have received two doses of a vaccine though it is unclear whether any of those affected have underlying health conditions.

Asked on BBC Breakfast about the target to offer every UK adult a booster jab by the end of the month, Mr Javid said: “I hope it is (achievable).

“We’re going to throw everything at it.

“What we’ve learnt about this new variant, Omicron, in the past week is, first of all, it’s spreading at a phenomenal rate.

“The number of infections is doubling every two or three days, there’s going to be a tidal wave of infection.”

Number 10 later said some people will be able to get their booster dose of the vaccine on Christmas Day.

The Prime Minister’s official spokesman said: “My understanding is that there will be appointments available on Christmas Day, and obviously the NHS will monitor what the demand is.

“There was, for example last year, the NHS was open for vaccinations on Christmas Day, which we didn’t see a huge demand (for) on Christmas Day.”

But he added: “Should individuals wish to come forward, we will make sure there is capacity.”