Boris Johnson will bring in the Army to help roll out 'rapid turnaround tests' which will see 'whole cities' able to tested for Covid within days.
Government scientific advisers have endorsed Mr Johnson's £100billion Operation Moonshot, which would see 10 million people tested a day regardless of whether they have symptoms, in a paper submitted to Downing St last month.
Population-wide testing has the ability to slash Covid-19's reproduction rate in half, the experts said.
Boris Johnson will bring in the Army to help roll out 'rapid turnaround tests' which will see 'whole cities' able to tested for Covid within days
Key points in COVID lockdown Mark 2
Britain's overall R rate - the average number of people each Covid-19 patient infects - is estimated to be as high as 1.5, which has sparked the PM into launching fresh action tonight.
SAGE suggested the R could be shrunk to at least 0.75 with mass testing and a better contact tracing regime.
At the moment, NHS Test and Trace - once hailed as 'world beating' by ministers - is still failing to find four in 10 suspected Covid-19 cases, and often doesn't reach them for at least three days.
Experts say squashing the R rate hinges on a 'well-functioning test and trace system' that catches at least 80 per cent of close contacts of infected patients within a day.
Outlining progress in the testing programme, Mr Johnson said tonight: 'We now have the immediate prospect of using many millions of cheap, reliable and above all rapid turnaround tests.'
He said these will 'drive down the disease', the Army has been brought in to assist the logistics and a rollout will begin in a 'matter of days'.
'Over next few days, weeks, we plan a steady but massive expansion in the deployment of these quick turnaround tests, applying them in an ever-growing number of situations from helping women to have their partners with them in labour wards when they're giving birth, to testing whole towns and even whole cities,' he said.
Professor of cellular microbiology, Dr Simon Clarke, described the announcement as 'hurried', which 'may have been announced now purely as a way to provide some sugar along with the bitter medicine of lockdown'.
However, he added: 'mass rapid and effective testing and isolating of infected people really is the best way for the country to get out of this nightmare.'
Businesses and politicians have urged the Government to use the four-week 'Stay at Home' period to maximise the effectiveness of test and trace systems.
British Chambers of Commerce director general Adam Marshall said: 'The Government must not squander the time afforded to them through another lockdown to enable mass testing and fix test and trace systems - which hold the key to a lasting exit strategy for both public health and the economy.'
Those sentiments were echoed by London mayor Sadiq Khan who said: 'We must once again make huge collective sacrifices now in order to prevent even greater suffering later. I will continue to lobby the Government to finally sort out a fully functioning test and trace system and the financial support London needs.'
The Government had pledged that there would be a capacity of 500,000 tests per day by the end of this month, and it will not be known if this has been achieved until Monday.
The latest data on the dashboard from Thursday shows that there is currently a capacity for 480,961 tests - with 347,626 tests actually being processed.
The Prime Minister made the announcement at a Downing Street press conference this evening, as he plunged the nation back into a full lockdown until December 2
The PM effectively took the country back to square one tonight as he unveiled the dramatic new national month-long lockdown to avoid a 'medical and moral disaster'.
After weeks insisting he is sticking to local restrictions, he completed a humiliating U-turn by announcing blanket coronavirus restrictions for England at a prime-time press conference alongside medical and science chiefs Chris Whitty and Patrick Vallance.
Mr Johnson said the draconian measures - which come into force from midnight Thursday morning until December 2 - were the only way to avert bleak Sage predictions of 85,000 deaths this winter, far above the previous 'reasonable worst case', and the NHS being swamped before Christmas. He said otherwise doctors would have to choose between saving Covid sufferers and those with other illnesses.
'No responsible PM can ignore the message of those figures,' Mr Johnson said. 'We've got to be humble in the face of nature.'
Mr Johnson pointed out that the action was not the same as March as key sectors of the economy are under orders to stay open, but said he was'under no illusions' about how tough it would be.
He declared that the furlough scheme will be extended for the period, rather than ending tomorrow as originally planned.
He also refused to rule out extending the measures beyond the proposed end date. Asked if the time would be enough, the premier said: 'I hope so. We have every reason to believe it will be. But we will be driven by the science.'
Reviving the government mantra from the height of lockdown, Mr Johnson urged the public: 'Stay at home, protect the NHS and save lives.'