New cases of coronavirus could be hitting 6,000 a day in England, with “clear evidence” of a rise in positive tests in the under-35s, according to the Office for National Statistics.
The ONS found infection rates were higher in the North West and London, based on random testing of thousands of people in households.
The figures are for the week to 10 September.
New England-wide measures could soon be brought in to reduce cases.
This follows a sharp rise in new daily UK lab-confirmed cases to 3,395 over the last two weeks and ongoing problems with the government’s test and trace programme, leading to people struggling to access tests.
Cases of the virus and hospital admissions for Covid-19 are now thought to be doubling every seven to eight days in the UK.
The Covid Symptom Study app, which tracks the health of four million people in the UK, estimates there are around 7,500 new cases of Covid every day over the last two weeks.
Their latest figures show a rise in cases in London for the first time since June.
Prof Tim Spector, professor of genetic epidemiology at King’s College London and app founder, said it was “a worrying picture”, adding it appears “to be the start of a second wave”.
The ONS infection survey, which has been producing weekly estimates of virus cases since April, tests people whether they have symptoms or not.
This makes it one of the most accurate pictures of levels of infection in England and Wales, although it still has a considerable margin of uncertainty.
Its latest figures are based on more than 200,000 swab tests taken over the last six weeks.
Out of 136 positive tests, children aged two to 11 and young people aged 17 to 34 had the highest infection rates.
Data from Wales suggests Covid-19 case there are currently “relatively stable” - with an estimated one in 2,000 people testing positive.
But the ONS said the results in Wales should be interpreted with caution because of the small number of tests in the sample.