Boris Johnson has told Brits "your tier is not your destiny" after an angry backlash over plans to plunge most of England into tough new restrictions.
The Prime Minister told a Downing Street press conference that "every area has the means of escape" from the top levels of restrictions.
Mr Johnson said he was "sorry" about about the pain inflicted on businesses and residents when they move into Tier 2 and 3 areas next week.
But he added: "If we ease off now, we risk losing control over this virus all over again, casting aside our hard-won gains and forcing us back into a New Year national lockdown with all the damage that would mean."
More than 55 million people in England face tough coronavirus curbs after the national lockdown lifts on December 2.
Around 99% of England will be plunged into the top two tiers of restrictions, with bans on meeting family and friends indoors.
Only the Isle of Wight, Cornwall and the Scilly Isles have been placed in the lowest Tier 1 category - around 1% of the population.
Setting out the new measures, Mr Johnson said: "I know this will bring a great deal of heartache and frustration especially for our vital hospitality sector.
"I really wish it were otherwise but if we are going to keep schools open, as we must, then our options in bearing down on the disease are necessarily limited.
"There is no doubt that the restrictions in all tiers are tough and I am sorry about that."
Mr Johnson sought to dampen a furious backlash from MPs in his own party over the broad brush decisions on tiering, which some entire counties plunged into tough restrictions.
He said: "The allocation of tiers will be reviewed every 14 days starting on December 16.
"So your tier is not your destiny. Every area has the means of escape.
"I have no doubt that together we can get through this winter, suppress the virus until vaccines come to our aid and then reclaim our lives and all the things that we love."
Mr Johnson pointed to the mass testing pilots in Liverpool, which has seen cases fall, allowing the city region to become the first place to move down from Tier 3 to Tier 2.
"This is a success story which we want other parts of the country to replicate so we will work with local government, public health leaders and our fantastic Armed Forces, to offer community testing to tier 3 areas as quickly as possible, opening the way for them to follow Liverpool’s example," he said.
But Labour's Deputy Leader Angela Rayner branded his comments as "patronising guff".
The Ashton-Under-Lyne MP tweeted: "Your Tier is not your destiny'. I really wish Boris Johnson would just stop it with this patronising guff.
"My constituents have been in local lockdown since July and you still haven't explained to them the actual criteria for going into Tier 3 and how we can leave Tier 3."
Former Tory Chief Whip Mark Harper also expressed scepticism about the claims.
Mr Harper, whose Forest of Dean constituency is in Tier 2, tweeted: "Unfortunately, just after the PM said this, Chris Whitty, the chief medical officer, said Tier 2 would only hold infections level, and Tier 1 would see them go up.
"That rather suggests if you're in Tier 2, it is your destiny - at least until the spring."
Mr Johnson's top advisors pointed to flaws in the previous tiers system, which the Government SAGE experts have already said were not strict enough.
Chief scientific adviser Sir Patrick Vallance said the previous tier system had failed to suppress the infection rate properly.
He said: "The message is that the tiers worked in terms of slowing but didn't work in terms of flattening and reversing it.
"The national lockdown looks as if it has flattened it and is sending it downwards and it is important we do bring it down because numbers remain high."
England's Chief Medical Officer Professor Chris Whitty said Tier 1 would still lead to an increase in infections.
He said: "Tier 1, which is very similar to the previous Tier 1, slowed things down but did not stop the rise anywhere.
"So the reason why Tier 1 at this time of year, with the current measures we currently have before we have any vaccines, is relatively limited is almost certainly anywhere going into Tier 1 will rise and the only places that are there are places with very low rates at the moment."
Asked whether the approach was really working, Mr Johnson said: "On your question about the whole local versus national lockdown strategy, actually I think if you listen to what Patrick (Vallance) said earlier on, the tiered approach was delivering, it was slowing the virus down and that's why a tiered, reasonable approach is the right way to go now.
"If you look at the disparity in instances between some places in some parts of the UK and others, you want to go for a tiered approach."
He said mass community testing was the "real change" and signalled it was the way out of Tier 3 restrictions.
Meanwhile, Prof Whitty also delivered a stark warning to the nation not to hug and kiss their elderly relatives when the rules are relaxed at Christmas.
He said: "Would I want someone to see their family? Of course, that's what Christmas is about, whether people celebrate Christmas as a festival themselves or from any other belief system. It is an opportunity for families.
"But would I encourage someone to hug and kiss their elderly relatives? No, I would not.
"It is not against the law - and that's the whole point. You can do it in the rules that are there but it does not make sense because you could be carrying the virus and if you've got an elderly relative, that would not be the thing you want to do in the period where we're running up to a point where we might be able to protect older people.
"I think people just have to have sense and this is very much what I think people will do."
