Boris Johnson has announced tougher Covid-19 measures in England to control the spread of the Omicron variant
Guidance to work from home will return on Monday and face masks will also have to be worn in more public venues
Covid passes proving vaccination or a negative test will be required at nightclubs and venues with large crowds
The Plan B restrictions are "proportionate and responsible", the PM says
Health Secretary Sajid Javid meanwhile tells the Commons that Omicron is much more transmissible than the Delta variant
Earlier the PM apologised for a video that showed his staff joking about a Christmas party held during lockdown last December and ordered an inquiry
The Met Police has said it will not investigate the video because it does not "provide evidence" regulations were breached
Allegra Stratton, who was Johnson's spokeswoman at the time, has resigned from No 10 over the video
The PM says the first step will be to reintroduce the guidance to work from home, which will come in from Monday in England.
"By reducing your contacts in the workplace you will slow transmission," he says.
Prime Minister Boris Johnson says it is now "proportionate and responsible" to move to Plan B measures in England.
Boris Johnson begins by saying that the government acted as soon as the Omicron variant was discovered.
He says we still do not know the full details of the virus, but it is becoming clear that it is spreading rapidly.
He says the true number of Omicron cases in the UK will be much higher than those confirmed cases.
The news conference has started and Prime Minister Boris Johnson is making his opening remarks.
Stick with us for all the latest updates and analysis.
Health Secretary Sajid Javid is updating MPs in the House of Commons at the same time.
Image source, UK Parliament/Jessica Taylor/PA MediaIt's been a busy day, so while we wait for the news conference here's a quick reminder of what's happened so far:
Iain Watson
Political correspondent
A No 10 press conference had been pencilled in for today to mark the anniversary of the first jab being delivered in to Margaret Keenan's arm.
Sources were suggesting yesterday that the focus of the event would be "jabs, not regs".
In other words, the booster programme and the progress of the pandemic - and not, at this stage, new restrictions.
It looked like restrictions might be on the way when the more transmissible nature of the Omicron variant was reported to the Cabinet yesterday. But sources were suggesting more data was needed.
If more measures are announced tonight, certainly some of Boris Johnson's own MPs are sceptical about the timing - on the day that the Downing Street party has dominated the headlines.
One - William Wragg - said publicly this was a diversionary tactic.
Privately others share those concerns, with one telling me the timing was "very odd" and another incredulous that a press conference was going ahead.
That said, as more is known about the new variant, the government can argue that it would be irresponsible not to act and that people will be more interested to know what will happen this Christmas.
Image source, PA MediaIn the next 10 minutes we're expecting a Downing Street news conference on Covid, led by Prime Minister Boris Johnson.
He'll be joined by England's Chief Medical Officer Prof Chris Whitty and Chief Scientific Adviser Sir Patrick Vallance.
It comes after ministers met to consider moving to Plan B measures to tackle the Omicron variant in England, including advice to work from home, tougher rules on masks and some form of Covid certification.
James Gallagher
Health and science correspondent, BBC News
Image source, Getty ImagesMultiple studies have now shown Omicron is better than other variants at evading part of the immune system.
But what does this mean?
The studies have focused on neutralising antibodies that stick to the virus and stop it infecting our body's cells.
If these are less effective then it could increase the chances of you catching Covid, but it is far too soon to quantify how likely that is to happen.
There are also signs that a third dose or a mix of past infection and vaccines would minimise the risk.
The vaccines are still highly likely to protect most people against severe disease because they train far more of the immune system than just neutralising antibodies.
T-cells, which kick in once an infection is under way, also play an important role - they are better at dealing with variants as they can attack different parts of the virus.
Boris Johnson will be joined at the Downing Street news conference at 18:00 by Prof Chris Whitty, England's chief medical officer, and Sir Patrick Vallance, chief scientific adviser.
Health Secretary Sajid Javid will also address the Commons on Wednesday evening, it is understood.
Ministers have met to discuss whether to move to the government's Plan B measures for the winter.
The Covid Operations Committee is believed to have discussed new guidance on working from home, further rules on masks and some form of Covid certification earlier today.
Rachel Glennon, whose father died with Covid on 22 December last year, says the revelations about the Downing Street Christmas Party have "deepened the shock and grief" in the run up to the anniversary of his death.
“Whilst we were watching our loved one gasping for breath over Facetime, there was obviously a complete disregard for the rules by those that were making them," she tells the BBC.
“I couldn’t see my dad, my mum couldn’t say goodbye and people were at parties that were making these rules," she says. "They should have been leading by example and they weren’t.”
The prime minister earlier told MPs he was "furious" about the video featuring Allegra Stratton and that he had been "repeatedly assured" no party had taken place. He has ordered an inquiry and said any rule-breakers would be punished.
We've been hearing from lots of readers, listeners and viewers about the issue. Sandy from Thame tells us she feels the video surfacing now is "just political point-scoring".
She says the video was relevant a year ago and it was "bad taste" to hold a party at the time, but politicians were "technically working".
The prime minister will hold a Covid news conference at 18:00 GMT, a No 10 spokesperson says.
We'll bring you all the updates right here.
Nick Garnett
North of England reporter
WATCH: The video that Allegra Stratton has now resigned over
People out and about in Huddersfield have also been sharing their views on the party - and the video of No 10 staff joking about it.
"I'm sick to death of all of them," says 41-year-old Kirsty, who's on a day out with her mother. It's the first time they've been out together since lockdown was lifted.
"I don't go out. I still don't go out. Really, this is very rare," says Kirsty, who runs a haulage company.
"I just think it's unfair. If they ask you to do something, you gotta follow the rules and do it. But why don't they follow the same rules?"
Her mother Susan, 70, talks about watching Allegra Stratton - who has now quit - grappling with awkward mock questions in the video.
"She doesn’t know what to say, she doesn’t want to lie does she?" Susan says.
Andria and Joyal think the party was hypocritical
Radio 1 Newsbeat has been in Uxbridge to hear what people in Prime Minister Boris Johnson's constituency think about the No 10 Christmas party saga.
"I don't approve at all because we were all away from our loved ones," says Joyal.
"Because they're in power, they think they can do whatever they want."
His friend Andria said she thought the party was "hypocritical".
Emilia thinks the government should set an example
Of course, not everyone was following the lockdown rules in December last year and it wasn't just Downing Street staff having parties. But Emilia says it's different when it comes to government.
"It's not an excuse that the public were basically doing the same thing," she says.
"They're the government. He's the prime minister. It makes us, especially young people, take him less seriously."
Amid that flurry of news the daily coronavirus figures have been published.
A further 51,342 new Covid cases have been confirmed across the UK, up from 45,691 yesterday and 48,374 for the same day last week.
There have also been 161 deaths within 28 days of a positive test reported across the UK.
It means there have been 339,861 new cases in the last seven days, an 11.3% rise on the previous seven-day period.
A further 391,050 booster doses were given on Tuesday, taking the proportion of over-12s who have now had a booster to 37%.
Image source, PA MediaQuote MessageThe British people have made immense sacrifices in the ongoing battle against Covid-19, I now realise my comments in the leaked video of 20 December last year have become a distraction in that fight. My remarks seemed to make light of the rules, rules that people were doing everything to obey. That was never my intention. I will regret those remarks for the rest of my days and I offer my profound apologies to all of you at home for them.
Quote MessageWorking in government is an immense privilege. I tried to do right by you all, to behave with civility and decency and up to the high standards you rightly expect of No 10. I will always be proud of what was achieved at COP26 in Glasgow and the progress that was made on coal, cars, cash and trees. This country and the prime minister's leadership on climate change and on nature will make a lasting difference to the whole world. It has been an honour to play a part in that. I understand the anger and frustration that people feel.
Quote MessageTo all of you who lost loved ones, who endured intolerable loneliness and who struggled with your businesses, I am truly sorry and this afternoon I am offering my resignation to the prime minister.
Allegra Stratton
Allegra Stratton offered her "profound apologies" in an emotional statement outside her home.
"My remarks seemed to make light of the rules, rules that people were doing everything to obey.
"That was never my intention. I will regret those remarks for the rest of my days and I offer my profound apologies to all of you at home for them."
Downing Street party: Allegra Stratton joked at a mock press conference
Allegra Stratton's resignation comes after the leaking of a Downing Street video showing her taking part in a jokey exchange from behind a lectern in Downing Street, while answering practice questions from another member of staff, Ed Oldfield.
When this was recorded, Stratton, a former Guardian and BBC journalist, was gearing up to become the face of daily televised government briefings. The plan at the time was for her to take questions on-camera, as happens with White House briefings in the US.
But the government decided not to go ahead with these and Stratton moved to being in charge of publicity for the COP26 climate change conference in Glasgow in October and November. Stratton is married to James Forsyth, political editor of the Spectator magazine.
She became involved in a Downing Street power struggle last year that ended in the departure of communications director Lee Cain and the PM's most senior adviser, Dominic Cummings.
Making her resignation statement through tears, Allegra Stratton said she had become a distraction in the fight against Covid because of her comments in the video.
She said the British people had made immense sacrifices and apologised for comments that "seemed to make light of the rules".
"I will regret those remarks for the rest of my days and offer my profound apologies to all of you for them," she said.
Allegra Stratton has just told broadcasters outside her house that she has resigned after the publication of the leaked video that showed her joking about a party at Downing Street last Christmas.
Earlier Boris Johnson said he was "furious" about the video and that he had been "repeatedly assured" that no party took place.
The BBC has been told that dozens of people attended the party at No 10 during lockdown.
BioNTech and Pfizer said that three doses of their vaccine can neutralise the new Omicron variant.
Three doses provide a similar level of antibodies against Omicron to that of two doses with other variants.
The manufacturers of the Covid vaccine announced the results of the small study on Wednesday.
They said that if needed, they could deliver an upgraded version of their vaccine by March next year.
"Ensuring as many people as possible are fully vaccinated with the first two dose series and a booster remains the best course of action to prevent the spread of Covid-19," Pfizer boss Albert Bourla said in a statement.
It comes after the World Health Organization said existing vaccines should still protect people who contract the Omicron variant from severe Covid cases.