Coronavirus infections in England are doubling every week and the reproduction 'R' rate could be as high as 1.7, according to a Government-led study.
Experts who have been swabbing tens of thousands of people in England during the crisis found an estimated 13 people per 10,000 were infected between August 22 and September 7, compared to four people per 10,000 between July 24 and August 11.
The scientists behind the Imperial College London REACT-1 study said the findings showed the epidemic is doubling in size every 'seven to eight days'. By comparison, Covid-19 infections were increasing by twofold every three days at the start of the crisis.
NHS England today confirmed nine more deaths from coronavirus while none were announced by Scotland, Wales or Northern Ireland.
The Imperial findings were published as the Government prepares to impose its new 'rule of six' social gathering restriction from Monday which outlaws groups of seven or more people from meeting up indoors and outdoors.
Health Secretary Matt Hancock said today's data justifies the rule, which had been triggered by soaring numbers of cases among people in their teens and 20s.
Boris Johnson is hoping it will help to get the virus back under control but there is a growing Tory backlash because while children will be exempted in Scotland and Wales, they will be subject to the restriction in England in a move which critics argue will make many family reunions impossible.
Senior Conservatives have labelled the rule 'absolutely grotesque', accusing the Government of an unacceptable assault on personal freedom and liberty. They have also criticised ministers for imposing the measure without any debate or vote in Parliament.
The rule was agreed at a meeting of the Government's coronavirus strategy committee earlier this week but a string of senior ministers were opposed to it.
A Cabinet source claimed Matt Hancock had driven the decision to adopt the restriction but allies of the Health Secretary said it was wrong to characterise the meeting in such a way.
However, Mr Hancock today jumped on the Imperial findings and said they demonstrated that 'the pandemic is not over' as he urged people to stick to the new social gathering rule.
He said: 'It's so important that everyone abides by the law and socialise in groups up to six, make space between you and those outside your household, get a test and self-isolate if you develop symptoms and wash your hands regularly.'
Despite the surge in cases, the overall prevalence of the virus is still much lower now than it was back in March - about 3,000 people were estimated to be getting infected every day this week compared to 100,000 a day six months ago.
The latest statistics mean it would take several months for the outbreak to escalate to a level similar to that seen during the peak of the first wave.
The seven-day average number of people testing positive for the coronavirus has spiked sharply, rising from 860 on August 10 to more than 2,000 this week
This is echoed by data from the Covid Symptom Tracker app, run by King's College London scientists, which predicts there are 3,610 new cases each day across the whole UK
The number of people testing positive through the Government's swabbing programme has been on the rise since early August but scientists initially thought the rise was being driven by more tests being conducted
The REACT-1 findings were one of the main driving forces behind Mr Johnson's decision to tighten lockdown restrictions with a number of other Covid-19 surveillance studies observing similar sudden increases in the number of people testing positive.
The Imperial-led study found that out of 152,909 swab results collected at the start of September, 136 were positive, and prevalence doubled every 7.7 days.
Professor Paul Elliott, director of the REACT-1 programme at Imperial, said: 'I think the really important thing here is that this system was set up as an early warning system. And I think it has picked up the signal early. And that's being fed in to Government.'
Professor Elliot and his team estimated the R rate - the average number of people each coronavirus patient infects - was 1.7 in England between the end of August and start of September - the highest level since mid-March.
The Imperial team is just one of several research groups monitoring the reproduction rate. The Government's Scientific Advisory Group for Emergencies (SAGE) makes its own R value predictions every week based on different data and modelling.
Its latest report suggests, for the UK as a whole, the R number could be as high as 1.2. But SAGE has admitted that its estimates about R are three weeks behind due to lags in the way it records its data, meaning the estimate may not reflect the current trajectory of the crisis.
When the R is above one an outbreak can start to grow exponentially so keeping the figure below that level is deemed crucial in containing the disease.
The Office for National Statistics said today it estimates at least 3,200 people are getting infected each day. This is a surge of 1,000 per day from the 2,200 it estimated last week. This is echoed by data from the Covid Symptom Tracker app, run by King's College London scientists, which predicts there are 3,610 new cases each day across the whole UK.
Professor Elliott added: 'The prevalence is still quite low. It's higher than it was in our second round, which was coming into June and July, so it's gone back up. It was very high, we had the lockdown, it came down during May, continued to go down into August into really quite low levels. Now it's gone back up again.'
Prime Minister Boris Johnson hopes the new lockdown rule of six will help to get the coronavirus back under control but there is a growing Tory backlash because while children will be exempted in Scotland and Wales
The Office for National Statistics, a Government-run agency, said today it estimates at least 3,200 people are getting infected each day. This is a surge of 1,000 per day from the 2,200 it predicted last week
Official SAGE data today showed the R rate was definitely 1 or higher in England and in most regions
Birmingham has been hit by a new lockdown meaning people will be banned from mixing with anyone outside their own household from Tuesday.
West Midlands mayor Andy Street announced the measure today.
It comes as the number of coronavirus patients being admitted to hospital in the city is doubling every week.
Seven people are fighting for their lives in intensive care with the disease and 68 are on wards at the Queen Elizabeth and Heartlands NHS hospitals, according to local reports.
And hundreds are testing positive for the virus every week, meaning many could be just days away from needing hospital care.
The mayor said this afternoon: 'The following areas will now be escalated to an area of national intervention, with a ban on people socialising with people outside their own household.
'The ban will take effect from Tuesday 15th September, but residents are advised to avoid household mixing before then as it has been identified as one of the drivers of