The UK government is said to be considering a 'Covid Plan D' in England if hospitals become overwhelmed.
With concerns rising over the Omicron variant, Number 10 is reportedly looking at options if the spread becomes unmanageable.
A Whitehall insider told the Mirror that this could see pubs and restaurants restricted to outdoor service or even closed all together.
Experts predicted earlier this week that the UK could see one million cases of the Omicron variant by the end of December.
And officials are said to be drawing up plans for 'Plan C' and even a 'Plan D' to deal with it.
Under 'Plan C', we could see the return of the NHS Covid app check-in for pubs and restaurants, with face masks made compulsory for all indoor spaces.
According to reports, Covid passports could also be made mandatory for more venues and those who come into contact with a positive Covid case will be ordered to isolate for 10 days.
Under the current guidelines, people who have received both doses of the vaccine only have to isolate if they come into contact with someone who has been infected by the Omicron variant.
Despite the reports, however, when asked by the Mirror if 'Plan C' had been officially drawn up yet, a spokesperson for the Prime Minister said: "Not that I'm aware of."
However, they confirmed that more measures were being looked into in case the situation worsens.
They added: "As a responsible Government, of course, you would expect us to... we have an array, already, of options available to us in terms of what measures we can take to mitigate a growth of any variant or virus.
"But there are no plans to go beyond that currently."
This comes after the UK Health Security Agency (UKHSA) warned that two doses of the Oxford/AstraZeneca and Pfizer/BioNTech vaccines provided 'much lower' levels of protection against Omicron than the Delta variant.
The body said, however, that the booster jabs increased protection to between 70 and 75 percent.
Dr Mary Ramsay, head of immunisation at the UKHSA, said: "These early estimates should be treated with caution but they indicate that a few months after the second jab, there is a greater risk of catching the Omicron variant compared to Delta strain.
"The data suggest this risk is significantly reduced following a booster vaccine, so I urge everyone to take up their booster when eligible.
"We expect the vaccines to show higher protection against the serious complications of Covid-19, so if you haven’t yet had your first two doses please book an appointment straight away."
Parliament is set to vote next week on the government's proposed 'Plan B', with the use of Covid passports being required for large venues and face masks for 'most public indoor venues'.
If it is passed, it will also see people asked to work from home if possible and close contacts with Covid cases to test daily for seven days.
Despite concern on the Tory backbenches, Labour leader Sir Keir Starmer has confirmed that he will vote for the measures.
As a result, they are expected to be given the green light.
LADbible has contacted Number 10 for a comment.
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