Scientists at Cambridge estimate that R is now 1.04 in the southwest, whereas two weeks ago its rate was the second lowest. It is 1.02 in the southeast, where the rate was 0.92 a fortnight ago.
Other areas have R-rates of 0.9 or more: in the North East and Yorkshire the rate is 0.90 and in the North West and London the estimated rate is 0.92 .
Niall Dickson, chief executive of the NHS Confederation, which represents hospitals and other health services, said senior officials were extremely concerned that an increase in cases was imminent.
He told the All-Party Parliamentary Group on the Coronavirus: ‘I would say in regards to the second peak issue … the levels of concern among our members – the people who run the NHS trusts, who run primary care and at all levels. in systems – is very high.
Scientists said removing lockdown measures meant Britain was now “facing a return to community transmission”.
Professor Jose Vazquez-Boland, president of infectious diseases at the University of Edinburgh, said further spikes in incidence were likely on the horizon.
He said: “We are facing a return to community transmission after the lockdown measures are removed. It should be clear that the effectiveness of interlocks is only temporary.
“There will be a resurgence of new cases any time social restraint measures are lifted as long as the virus remains in circulation.”
Professor James Naismith, director of the Rosalind Franklin Institute, said without better case isolation Britain could face “an ongoing tragedy”.
He said: “We and other countries are detecting young people with Covid-19, in February we never noticed them. It seems likely that the virus first spreads in this group, but with few symptoms and little disease.
“We know the virus will spread over time from young to old / more vulnerable [people] where we will see hospitalization, serious illness and death. It will happen in a few weeks if we don’t remove the virus.
On Tuesday Mr Johnson said: ‘It is clear that we are now facing, I am afraid, the threat of a second wave in other parts of Europe and that we just need to be vigilant.
A Downing Street spokesperson said: “The Prime Minister is clear that we must remain vigilant and continue to follow official guidelines to keep the virus under control and prevent any second waves. ”
The health secretary will say on Thursday that the government is looking at ways to reduce the 14-day quarantine period.
It follows research which shows that if arrivals are tested one week after arrival, 94% of Covid-19 cases are identified, which makes it possible to limit isolation to eight days.
On Thursday, Matt Hancock is expected to signal his willingness to reduce quarantine times, but is not expected to commit to a specific time frame.
Ministers are in talks with airport chiefs, after the Heathrow boss urged them to introduce testing for arriving passengers.
Research from the London School of Hygiene and Tropical Medicine indicates that an eight-day quarantine, supported by seven-day testing, would identify 94% of cases. A six-day quarantine supported by testing would detect 88% of infections, he said.