Scientists warn it's too early to ease lockdown amid fears of crowds gathering over warm weekend
Scientists Sir Jeremy Farrar and Professor John Edmunds, both members of the Scientific Advisory Group for Emergencies (Sage) - which advises the Government on the Covid-19 - said ministers were taking risks by following their current plans.
They expressed concern at allowing the gradual reopening of shops and schools and larger gatherings to meet in private while the number of new cases each day remains "relatively high".
Sir Jeremy also said the newly-introduced NHS test-and-trace system needed to be "fully working" before measures were eased.
Meanwhile, a tranche of papers released by Sage revealed advice given to the Government in April said it was "likely" the R-value - the average number of people that will contract coronavirus from an infected person - would go above one should non-essential shops be reopened.
The comments come as Britain is set for a weekend of high temperatures and police have urged the public to follow current safeguards about social contact ahead of the lessening of restrictions, which will allow up to six people to meet outside if social distancing is observed.
In a Twitter post, Sir Jeremy said: "Covid-19 spreading too fast to lift lockdown in England. Agree with John & clear science advice.
"TTI (test, trace and isolate) has to be in place, fully working, capable dealing any surge immediately, locally responsive, rapid results & infection rates have to be lower. And trusted."
A document on a Sage meeting from April 13, released on Friday, showed the Scientific Pandemic Influenza Group on Modelling (SPI-M) that advises the Government warned against reopening shops and leisure facilities.
The document said: "There is limited evidence on the effect of closing of non-essential retail, libraries, bars, restaurants, etc, but it is likely that R would return to above 1 and a subsequent exponential growth in cases."
Downing Street warned the public that meet-ups remain prohibited until after the weekend.