The government has faced criticism over its handling of the pandemic and Johnson is wary of taking the brakes off too soon. Britain’s coronavirus death toll – 31,855 – is the second highest in the world, behind the United States.

With both the death rate and hospital admissions falling, it would be “madness” to allow a second spike in infections, he said.

But the decision to replace the government’s “stay-at-home” slogan, drummed into the public for weeks, was criticised by opposition parties who called the new “stay alert” message ambiguous.

Johnson said people should continue to work from home if they could, but those who cannot, such people working in construction and manufacturing, should be “actively encouraged to go to work”.

From Wednesday, people will be allowed to take unlimited amounts of outdoor exercise, he said, and can sit in the sun in their local park, drive to other destinations, and play sports with members of their own household.

Until now, people have been told only to exercise outdoors once a day and do so locally. Social distancing rules must still be obeyed, Johnson said, adding that fines would be increased for those who break them.

Johnson said he would set out further details to parliament on Monday, when a “roadmap” document will be published.

But opposition Labour leader Keir Starmer said Johnson had raised more questions than he had answered and there was now the prospect of different parts of the United Kingdom pulling in different directions.