Boris Johnson is set to announce a national lockdown next week after being warned it is the only way to save Christmas.
The Prime Minister reportedly decided on a shutdown after being warned the disease is spreading faster than the scientists' original 'worse-case scenario' prediction.
It is not yet clear how severe the lockdown will be or for how long it will last but some reporting has it lasting until December 1.
Labour leader Keir Starmer previously called for a circuit breaker national lockdown, although the Tories accused him of playing political games.
Responding to Mr Starmer's call in mid October, a senior government source said: “Keir Starmer is a shameless opportunist playing political games in the middle of a global pandemic.”
Now Sage experts believe the looming lockdown will have to last longer than two weeks to have the desired effect to protect the NHS and save lives.
A Cabinet source told Mail Online the shutdown will be announced next week.
The Government has repeatedly warned of the devastating economic consequences a second lockdown would have.
Scientists from the Sage committee told Mr Johnson and Chancellor Rishi Sunak the virus was set to kill 85,000 this winter.
Ministers were told to prepare for 500 deaths a day for at least three months, with more than 300,000 hospital patients, it is said.
The experts yesterday reportedly said this 'reasonable worst-case scenario' had already been passed.
They warned the Prime Minister it was too late for a 'circuit break' and called for a longer lockdown - like the month-long one that has just been announced in France.
The Government is now set to meet leaders of Scotland, Wales and Northern Ireland to agree a 'common approach' over Christmas.
It comes after Chief Medical Officer Professor Chris Whitty and Chief Scientific Adviser Sir Patrick Vallance warned all hospitals in England were on course to be full by December 17, Mail Online reports.