UK Health Secretary Matt Hancock has warned that London could be under a lockdown for months, as it will be "very difficult" to keep a highly infectious mutant strain of the novel coronavirus under control until vaccinations are rolled out.
His remarks on Sunday came just hours after the new Tier Four restrictions came into force in the British capital and parts of southeast England, reports Xinhua news agency.
The new tighter restrictions will be reviewed on December 30.
Hancock however indicated that it was unlikely they would be relaxed at that point.
"It is going to be very difficult to keep it under control until we have the vaccine rolled out," he told Sky News.
"We know with this new variant you can catch it more easily from a small amount of the virus being present.
"All of the different measures we have in place, we need more of them to control the spread of the new variant than we did to control the spread of the old variant.
"That is the fundamental problem," the Health Secretary added.
Hancock also criticized people who fled London before the new Tier Four lockdown came into force as "totally irresponsible".
"I think those scenes were totally irresponsible," Hancock said while speaking to the BBC later in the day.
"We have all got a responsibility. We in the government of course have a responsibility, but so does every single person.
"The plea that I have is that people will play their part because it is only by acting -- all of us -- that we can get this under control," he added.
On December 19, Prime Minister Boris Johnson effectively cancelled Christmas for more than 16 million people in London, south-eastern and eastern England as the region went into a new two-week lockdown on Sunday midnight.
Addressing a virtual briefing, Johnson said that the previous plan to allow up to three households to meet during five days around Christmas will have to be scrapped due to the discovery of the mutant strain.
An estimated 16.4 million people living in the new Tier Four areas, which include London and much of the surrounding region, will have to stay at home for a fortnight.
They will be barred from socialising with more than one person even outdoors, meaning no Christmas gatherings of entire families, while shops, leisure facilities, gyms, and hairdressers will be closed.
England was previously under a three-tier system.
London and parts of Essex and Hertfordshire had just moved into Tier Three on December 16 while some other areas in east and southeast of England entered Tier Three from December 19 following a rapid rise in infections in the area.
The UK has so far reported a total of 2,046,161 coronavirus cases since the onset of the pandemic earlier this year, while the death toll stood at 67,503.