Prime Minister Boris Johnson has said he will set out a “comprehensive” plan next week on reopening schools and restarting the economy.
In his first briefing since his return to work, the PM said the UK was “past the peak” of the coronavirus outbreak and “on the downward slope”.
But he stressed the country must not “risk a second spike” of the virus.
There have been 26,711 deaths in UK hospitals and the wider community, Mr Johnson said.
The prime minister said that “we can now see the sunlight”, but he insisted that to avoid the “disaster” of a second peak the UK must meet the fifth of five tests before the lockdown can be lifted.
“Nothing we do should lift the R or reproduction rate – back above one,” he said.
The BBC’s political editor Laura Kuenssberg asked what level the reproduction rate should be before the government would be “comfortable easing restrictions”.
The government’s chief medical officer, Prof Chris Whitty, replied: “We are absolutely confident that the wrong answer is anything over one.”
He explained that as soon as the R rises above one you “restart exponential growth” and “sooner or later” the NHS would be at the risk of being overwhelmed.
Mr Johnson said that keeping the reproduction rate down “is going to be absolutely vital to our recovery”.
Our correspondent also asked whether the economy “just has to wait” as the government continues with the lockdown in the UK.
The prime minister said it was “vital” to avoid a second peak “because that would really do economic damage”.
He added: “That’s why we’ve got to calibrate our measures so carefully and make sure that we not only unlock the economy gradually, but also find ways of continuing to suppress the disease.”
Mr Johnson also said face coverings will be “useful” as part of the strategy for coming out of lockdown “both for epidemiological reasons but also giving people confidence they can go back to work”.