British Prime Minister Boris Johnson has taken tentative steps toward easing the country’s near total lockdown, but he’s already facing criticism that his plan lacks clarity.

“We have been through the initial peak – but it is coming down the mountain that is often more dangerous,” Mr. Johnson said in a televised address Sunday evening.

Britain has been under lockdown since March 23, when Mr. Johnson closed schools, shops, restaurants and pubs, and ordered people to work from home if possible. The measures have helped slow the spread of the COVID-19 outbreak but the country still has more than 219,000 confirmed cases and close to 32,000 deaths, one of the highest death tolls in the world.

Mr. Johnson has been under growing pressure to ease some of the restrictions and kickstart the economy. Last week the Bank of England said Britain was on track for the worst recession in more than 300 years and three major airlines – British Airways, Virgin Atlantic and Ryanair – announced a total of 20,000 job cuts. Britain has also lagged behind several other European countries, including Italy, France, Spain and Germany, in lifting restrictions.

On Sunday, the Prime Minister outlined “the first sketch of a road map for reopening society.” Under the plan, people will be allowed to exercise more frequently outside their homes as of Wednesday and anyone working in construction or manufacturing will be encouraged to return to their jobs. Primary schools could open in June and by July. Mr. Johnson said parts of the hospitality industry could reopen, along with some public places.

The Prime Minister also announced that air travellers coming into Britain will soon have to go into quarantine, although he did not say for how long. Late Sunday the government said travellers from France would be excluded from the restriction. Britain has been among the few countries that have not imposed a 14-day quarantine for anyone entering the country. The aviation industry has bitterly opposed the quarantine, arguing that it will effectively end air travel and lead to tens of thousands of layoffs.

Mr. Johnson said more details will be released on Monday and he stressed that any further easing will depend on the rate of infection remaining low. To ensure that happens, he said the government would introduce a five-stage alert system – ranging from level one, which meant the virus had been eliminated, to level five, which meant the National Health Service had been overwhelmed. “We will be monitoring our progress locally, regionally, and nationally and if there are outbreaks, if there are problems, we will not hesitate to put on the brakes,” Mr. Johnson said, adding that the country was currently at level four.

The Prime Minister’s plans were met with skepticism from public-health experts and criticism from regional leaders who questioned why he changed the government’s key message from “stay at home” to “stay alert.”

“I don’t know what ‘stay alert’ means,” Scotland’s First Minister Nicola Sturgeon said Sunday. “My basic message for Scotland remains the same as it has been – please stay at home.” First ministers in Wales and Northern Ireland also said they would ignore the Prime Minister’s slogan and continue urging people to stay at home.

Health experts said Mr. Johnson’s plan was confusing and lacked detail. Trish Greenhalgh, a professor of primary care health sciences at the University of Oxford, said the strategy could end up hurting both the economy and public health. “Leaving aside who we’re allowed to play tennis with from Wednesday, this announcement seems to be pitching at a middle ground that could give us the worst of both worlds,” Dr. Greenhalgh said.

Jonathan Ball, professor of molecular virology at the University of Nottingham, said Mr. Johnson’s plan lacked a scientific underpinning. “I think the reality is, this is a statement driven almost entirely by an economic agenda and in truth lacks clarity in terms of future control of the virus epidemic,” he said.

However, business groups were more positive and said Mr. Johnson had finally outlined a way out of the lockdown. “Today marks the first glimmer of light for our faltering economy,” said Carolyn Fairbairn, director-general of the Confederation of British Industry. “A phased and careful return to work is the only way to protect jobs and pay for future public services.”

Several other countries have also adopted similar staged approaches to easing restrictions. As of Monday, most primary schools and businesses in France can reopen, but not cafes or bars. The government is also introducing “red” and “green” zones depending on infection levels. Spain is also allowing more businesses to open on Monday, including some bars and hotels in less-affected areas, and in Germany Bundesliga soccer games will resume on May 16.

However, there have been concern that lifting restrictions has resulted in an increase in infections. France has reported a new cluster of outbreaks, as have health officials in Germany and South Korea, where infections rebounded to a one-month high on Sunday.