One of the architects of lockdown has warned new coronavirus restrictions will be needed "sooner rather than later" to prevent the disease surging again.
Professor Neil Ferguson, from Imperial College London, said the UK was facing a "perfect storm" after controls eased over the summer.
"Right now we are at about the levels of infection we were seeing in this country in late February," he told the BBC Radio 4 Today programme.
"If we leave it another two to four weeks we will be back at levels we were seeing more like mid-March. That's clearly going to cause deaths because people will be hospitalised.
"I think some additional measures are likely to be needed sooner rather than later."
The warning came as Boris Johnson holds meetings with government officials amid fears the death rate could rise to the hundreds a day within weeks.
Labour deputy leader Angela Rayner also echoed calls by her leader Sir Keir Starmer for the prime minister to call a meeting of the Government's civil contingencies committee, known as Cobra.
"We are deeply concerned with the sharp rise in infection rates. What we have seen over the last six months is the Government still can't get the basics right,” she told Today.
"The Prime Minister has to convene a Cobra meeting this weekend. He has to look at the science and the evidence and he has to make sure the measures are in place and a clear communications strategy on that so people can do the right thing.
"It has been absolutely shocking to see how monumentally they have failed at the testing, tracing, tracking system that they put in place."
Wales' first minister Mark Drakeford also called for a Cobra meeting, telling Times Radio it was wrong that he had heard first about lockdown measures near the Welsh border, "on the radio".
Prof Ferguson called on ministers to develop a set of sustainable coronavirus restrictions to avoid repeated lockdowns.
The measures should be designed to last until a vaccine is in place, he argued.