In a televised address to the nation, Boris Johnson has unveiled a new Covid alert system and indicated how the UK could emerge from the lockdown.
The Prime Minister also said schools and non-essential shops will remain shut in England until at least June.
He said this is because the coronavirus transmission rate is still too high to significantly ease the lockdown.
"No, this is not the time simply to end the lockdown this week," he said. "Instead we are taking the first careful steps to modify our measures."
But Mr Johnson said people who cannot work from home should be "actively encouraged" to return to their jobs from Monday.
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He also granted unlimited exercise in England from Wednesday.
Mr Johnson outlined "the first sketch of a road map", with a new alert system to determine when aspects of the economy and social lives can be restarted as he tries to limit the damage.
After almost two months of lockdown, Mr Johnson set out what he called "the first sketch of a road map for reopening society".
Covid Alert System
A new Covid Alert System is being set up determined mainly by the reinfection rate and the number of cases.
The alert levels will be one to five and the higher the level, the tougher social distancing measures will have to be.
The Prime Minister said the UK had been in Level Four but "we are now in a position to begin to move in steps to Level Three".
Working from home
People who cannot work from home are being actively encouraged to go to work from tomorrow (Monday), instead of being told to only go if they must.
But they should avoid public transport if at all possible.
Unlimited outdoor exercise and visits to parks
From Wednesday, people are being encouraged to take unlimited amounts of outdoor exercise and even play sports, but only with members of their household.
Visiting and sunbathing in local parks will also be allowed as will driving to other destinations.
Social distancing remains - with bigger fines
But social distancing rules will still have to be obeyed with bigger fines for those who break them.
Schools may begin to reopen by June 1 at the earliest along with the phased reopening of shops.
And at least some pubs, restaurants, hotels and other public places could begin to reopen in July at the earliest "if and only if the numbers support it".
Row over messaging
Before his address to the nation, Mr Johnson provoked a row with the leaders of Scotland, Wales and Northern Ireland over his new "stay alert" slogan.
Scottish First Minister Nicola Sturgeon warned the "stay alert" messaging could be "catastrophic", as each of the devolved administrations said they would keep using the stronger "stay home" slogan.