The rule of six laws do not go far enough and the UK needs to take immediate action to stop households mixing, a government science adviser has warned.
Professor Calum Semple, a member of the government’s Scientific Advisory Group for Emergencies (Sage), said more measures are required to stop the spread of coronavirus.
On Tuesday, Boris Johnson will announce a 10pm curfew on all pubs, bars and restaurants in England, which will come into effect on Thursday.
As well as the early closing, establishments will be restricted by law to table service only.
Watch: What is the new ‘Rule of six’?
The prime minister is also considering other restrictions as COVID-19 case numbers in the UK continue to rise.
Another 4,368 new daily cases of coronavirus were reported in the UK on Monday, with 11 deaths.
On Tuesday, cabinet minister Michael Gove said plans for small numbers of fans to return to watch sporting events in England from the beginning of October had been shelved.
But Prof Semple, a professor of child health and outbreak medicine at the University of Liverpool, said neither the rule of six, which came into force earlier this month, nor the curfew will be sufficient measures on their own.
He told BBC Radio 4’s Today programme on Tuesday: “The time to act is now, we are in a serious situation, and the numbers that are rising are tracking the worse case scenario, so there is significant anxiety among the science and health community.”
He said the UK needed “quite a lot more” restrictions in place to halt the spread of COVID-19.
Asked if the rule of six is enough to stem the spread of coronavirus for the time being, he said: “I don’t really think so, I’m sorry to say.
“This is where it’ll hurt people most. I think we will get to a stage where people shouldn’t mix between households.
“The rule of six has been tried and not had time to kick in yet, but based on the numbers I’m seeing it doesn’t go far enough, so I do think we’ll be restricting inter-mingling between households.”
When asked if the incoming 10pm curfew for pubs and restaurants will be enough, Prof Semple replied: “No, it’s not going to be.
“There are several sectors of society that need to increase their restrictions, unfortunately - but it’s necessary, because we’re starting to see a rise in cases not just in the frail and elderly, but also in people under the age of 50.”
He added: “We’re going to have to see reductions in sporting events and that’s going to hit many of us hard.
“We’re likely to see restrictions on the hospitality sector and it’ll probably have to to go further than a 10pm curfew and table service only.”
Prof Semple said a study he runs on hospital cases in England, Scotland and Wales has shown a “rapid rise” in admissions, including an increase in people aged 20 to 40, particularly women.
“That suggests it’s community exposure in hospitality and care settings which we didn’t see before, probably because people under 50 are less invested in social distancing,” he said.
Watch: These were some of the most important moments from the COVID-19 briefing
The curfew on pubs and restaurants comes after the UK’s COVID-19 alert level was raised to four, meaning transmission is "high or rising exponentially".
On Monday, the government’s chief scientific adviser, Sir Patrick Vallance, said the number of new daily cases will reach 50,000 by mid-October if no action is taken.
This would, in turn, lead to 200 new daily deaths a month later in mid-November, he said.
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