LONDON — Prime Minister Boris Johnson said Tuesday that Britain has reached a "perilous turning point" in the coronavirus pandemic as he introduced new curfews on pubs and restaurants in England and encouraged remote working — restrictions that could remain in place for six months.

Johnson outlined a raft of new constraints aimed at reversing a spike in coronavirus cases. Starting Thursday, pubs and restaurants will offer table service only and have to close by 10 p.m. Johnson also said that if people can work from home, they should — an about-face from a previous push by the government for people to return to their workplaces and help revive city centers.

In addition, masks will be mandatory for retail workers, taxi drivers and bar and restaurant staffs, as well as customers when they are not seated at a table, the prime minister said.

The measures were more modest than many that reportedly had been under discussion, including a two-week mini-lockdown.

Johnson said the restrictions could remain in effect for “perhaps six months.”

Speaking in Parliament, he said that “as in Spain and France and many other countries, we have reached a perilous turning point.” The number of coronavirus cases in Britain has nearly quadrupled over the past month, he said.

The government also paused plans to allow spectators to return to major sporting events and halved the number of guests allowed at weddings to 15.

“Now is the time for us all to summon the discipline and the resolve and the spirit of togetherness that will carry us through,” Johnson said in a televised address to the nation — his third such speech during the pandemic. He also warned that restrictions may go further if they are ignored.

The new measures apply only to England. The semiautonomous governments in Scotland, Wales and Northern Ireland set their own rules. The biggest change in Scotland announced Tuesday was a ban on visiting other people’s households.

The curbs were unveiled a day after the government’s top scientists warned that coronavirus cases could spike to 50,000 per day by mid-October if the current rates — the virus is doubling roughly every seven days — continue on the same trajectory.

On Monday evening, the coronavirus alert status in Britain was raised from 3 to 4, meaning that transmission is “high or rising exponentially.”

Like countries across continental Europe, Britain is desperate to avoid a full-scale national shutdown akin to the one earlier this year that flatlined the economy.

Johnson stressed that this was not a “return to a full lockdown” like the one in March, when schools closed. “Nothing is more important than the education, health and well-being of young people,” he told Parliament.

Children in England returned to school in early September for in-person, full-time lessons. Attendance is mandatory.

The restrictions are a blow for Britain’s battered hospitality sector.

Until now, the government had been trying to encourage more people to go into offices where it was “safe” to do so. One survey suggested that Britons were far less keen than many of their European counterparts on returning to offices, a reluctance that has hurt local businesses.

Kate Nicholls, chief executive of UKHospitality, a trade association, said the new measures will “accelerate business closures and job losses.”

The British Beer and Pub Association said the new curfew would “devastate the pub sector” because “pubs were struggling to break even before today and these latest restrictions will push some to breaking point.”

The hospitality sector was already concerned about looming job losses as the government’s furlough program ends in October. Currently, the government is paying the majority of the salaries of nearly 10 million people.

Only last month, the government was actively encouraging people to dine out — even splitting the check with those who dined out on Mondays, Tuesdays or Wednesdays.

Some health experts questioned whether the government was going far enough with the latest restrictions.

Martin McKee, a professor of European public health at the London School of Hygiene and Tropical Medicine, said that the new restrictions were similar to those already in place at a local level in the English cities of Leicester and Bolton and that “those are showing a limited impact.”

“I suspect they have erred on the side of caution,” he said of the Johnson administration, “but none of us has a crystal ball.”