The government has been warned that relaxing the lockdown could see coronavirus deaths pass 100,000 by the end of the year.
A scientific adviser to the government reportedly said that if measures were relaxed too quickly it could spell disaster, adding that there is “limited room for manoeuvre”.
Projections carried out by the London School of Tropical Hygiene and Imperial College London put the death toll at six figures in some scenarios, according to The Sunday Times.
“Whether we get 100,000 deaths by the end of the year depends on how quickly measures are relaxed, how effective contact tracing is and whether we get on top of the situation in hospitals and care homes,” a government scientific adviser said.
“The care home and hospital epidemics seed infection back into the community via the staff employed in those institutions. We have to control them before significant relaxation will be possible.”
Prime minister Boris Johnson acknowledged the scale of the danger, saying "we'll have to work even harder to get every step right" now the peak is passed.
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"You have very few options on the climb up - but it's on the descent you have to make sure you don't run too fast, lose control and stumble," he told the Sun on Sunday.
On Monday, the government will publish a 50-page document outlining the full plan to cautiously re-start the economy to MPs after figures suggested the overall death toll for the UK has passed 36,500.
It comes as health officials have said they fear Britons are already starting to get complacent about the Covid-19 lockdown.
Traffic and mobile phone data collected this weekend has revealed more people are on the roads and looking for directions.
Professor Stephen Powis, national medical director of NHS England, said on Saturday that "there was a little bit of concern" after the unseasonably warm weather drew big crowds to public spaces.
Transport secretary Grant Shapps told the Downing Street briefing on Saturday that the PM would be proceeding with "extreme caution".
The incoming changes for England were only expected to be very modest, with a lifting the limit of only one form of exercise per day and to permit garden centres to reopen.
But in a toughening of measures, fines for those who fail to abide by the rules will be hiked.