People in England who cannot work from home are being encouraged to return to their workplaces, as the government begins easing some lockdown measures.
Transport Secretary Grant Shapps urged people to avoid public transport if possible to enable social distancing.
“This is a life and death situation,” he added.
Under the new rules, people can also spend more time outside, meet a friend at the park and move home, while garden centres can reopen.
Sports that are physically distanced – such as golf – are now permitted.
And two people from different households in England can meet in outdoor settings, such as parks, as long as they stay more than 2m apart.
Those who break the lockdown rules are to face tougher fines than before. However, new guidance issued by the College of Policing says officers have “no powers to enforce two-metre distancing” in England.
Government guidance on avoiding public transport and wearing face coverings in enclosed spaces is also “not enforceable” by police, the document states.
It follows a speech by Prime Minister Boris Johnson on Sunday in which he unveiled a “conditional plan” aimed at reopening society, much of which has been in lockdown for seven weeks.
This has led to a divergence in lockdown rules between the UK government and the devolved administrations, with Scotland, Wales and Northern Ireland keeping stricter measures in place and retaining the message to stay at home.
It comes as figures from the Office for National Statistics showed the UK economy shrank at the fastest pace since the financial crisis in the first quarter of 2020.
In England, employers have been issued with guidelines on keeping workplaces as safe as possible, including the use of staggered shifts and frequent cleaning.
And those who flout the rules could face criminal proceedings, the Health and Safety Executive watchdog has warned.
Frances O’Grady, general secretary of the Trades Union Congress, said the new guidelines for employers were “a step in the right direction” but “the real test will be delivery”.
She said employers should publish a risk assessment and if workers had any concerns they could contact the Health and Safety Executive hotline.
In other developments, estate agents can now reopen, viewings can take place and removal firms and conveyancers can re-start operations, so long as social-distancing and workplace-safety rules are followed.
Anyone who has already bought a new home will now be able to visit it to prepare for moving in.
About 450,000 people are estimated to have had their moving plans put on hold during the crisis, with property website Zoopla suggesting £82bn worth of deals have been stalled.
There was also news late on Tuesday for childminders who were told government guidance had been amended to allow them to reopen so long as they cared for children from just one household.
The updated lockdown regulations, which were presented to Parliament on Tuesday, also allow people to leave their homes to collect goods ordered from businesses or to travel to waste or recycling centres.
Some outdoor sports can get under way again, with golf clubs and tennis courts expected to reopen to the public. Playgrounds, however, will stay shut.
Restrictions have also been lifted on how far people can travel to get to the countryside, national parks and beaches in England.
However, people have been warned to respect local communities, keep their distance from others and avoid hotspots or busy areas.
The government is still advising people to only use public transport for essential journeys and reiterated that staying overnight at a holiday or second home was not allowed.
Those who break the rules will now face fines starting at £100 in England, and this will double on each further repeat offence up to £3,200.
National Police Chiefs’ Council chairman Martin Hewitt said officers would “continue to use common sense and discretion” in policing the new rules.