Ambitious mass testing plans that could keep hopes of Christmas parties alive would cost as much as £100 billion, according to reports.
Leaked documents seen by the BMJ suggest that the “Operation Moonshot” project – which would see millions of UK-wide tests carried out daily – could have a price tag close to that of the £114 billion budget given to NHS England in 2018/19.
Boris Johnson believes the scheme could help sport and entertainment venues reopen fully and allow people to socially mix in large groups again with on-the-day tests.
However, the plans previewed by Mr Johnson have been met with a mixed reaction from the health and scientific community, with concerns raised over the implications of a negative test result.
“In the near future we hope to start using testing to identify people who are negative, who don’t have coronavirus, who are not infectious.
“So we can allow them to behave in a more normal way in the knowledge they can’t infect anyone else with the virus,” the prime minister said at a Downing Street coronavirus update on Wednesday.
Watch Wednesday's coronavirus update in full:
England's deputy chief medical officer, Dr Jenny Harries, said the success of Moonshot would depend on how it is handled.
She told ITV’s Peston: “We do want to get back to as much normality as we can and any opportunity to do that through a new testing programme or using different testing technology is clearly a good thing to be following, but it’s not quite as simple as just doing that.”
Moonshot has received mixed reviews from the scientific community, including from Dr Chaand Nagpaul, council chairman of the British Medical Association (BMA), who said it was unclear how it would work given the “huge problems” currently seen with lab capacity.
“And the notion of opening up society based on negative tests of those without symptoms needs to be approached with caution – both because of the high rate of ‘false negatives’ and the potential to miss those who are incubating the virus,” Dr Nagpaul added.
Professor Jose Vazquez-Boland, chair of infectious diseases a University of Edinburgh, said: “The focus of testing currently remains on confirmation of suspected cases (people with symptoms), thus missing the point that most community transmission comes from those who are asymptomatic.
“Only a mass screening programme, such as this alternative plan announced by the Prime Minister, which involves the regular testing of all the population for asymptomatic transmitters, can keep Covid-19 under control and eventually lead to its eradication.”
Dr Joshua Moon, research fellow in the Science Research Policy Unit (SPRU) at the University of Sussex Business School, raised concerns about the plans.
He said: “A negative result could be that the individual is truly negative and therefore not infectious, or it could be that the individual is infected but early in the incubation period so isn’t testing positive yet, or it could be that the test itself didn’t capture enough viral material on the swab or saliva to test positive.
“In only one of these cases should the person be moving around as normal.”
Dr David Strain, clinical senior lecturer at the University of Exeter and chairman of the BMA’s medical academic staff committee, said: “The mass-testing strategy is fundamentally flawed, in that it is being based on technology that does not, as yet, exist.
“The Prime Minister’s suggestion that this will be as simple as “getting a pregnancy test” that will give results within 15 minutes is unlikely, if not impossible, in the timescale he was suggesting to get the country back on track.
“The worry is that comments such as these may undermine the credibility of some of the other very responsible measures that were announced, notably the halting of the larger social gatherings, delaying the reopening of large venues and moving the ‘rule of six’ from guidance to law.”
Ministers have faced increasing pressure in recent days over availability of tests, with many people reporting being sent hundreds of miles from home to get checked for the illness.
The new testing plans come as the prime minister admitted it was “too early to say” whether big parties could be held over the festive season this year.
Speaking on Wednesday, the prime minister hoped that “we could be able to get some aspects of our lives back to normal by Christmas” and pointed to mass testing as something which could help society open back up further.
Shadow Secretary of State for Foreign, Commonwealth and Development Affairs, Lisa Nandy said: "The Prime Minister is ignoring the very real problems in the system at the moment.
"If people can't even get a test when they've got symptoms and they've been asked to travel hundreds of miles at the moment, it's very difficult to have confidence that the government is going to be able to reach 10 million tests in capacity."
She added: "What we need right now is a sense of realism, we need the government to sort out the problems that have emerged with the system as it is."
For now, however, Mr Johnson urged people to limit their social contact “as much as possible” as he confirmed that social gatherings of more than six people will be outlawed in England from Monday.
Lockdown rules could also be tightened in other parts of the UK, as rates of Covid-19 infection have risen across the country in recent days.
Meanwhile the latest figures in the Government’s test and trace will be released on Thursday.
Last week, the number of close contacts of people who tested positive for Covid-19 being reached through Test and Trace was at its lowest since the system was launched.
On Wednesday, a further 2,659 positive cases were confirmed across the UK, taking the total up to 355,219.
Positive results have increased from from 12.5 per 100,000 people to 19.7 per 100,000 in the UK in the last week – with a particular rise in infections among young people.
Infections are most prevalent among the 19 to 21-year-old age group, with 54 cases per 100,000 people.
In Northern Ireland, it is expected that restrictions will be tightened on Thursday, while in Scotland, First Minister Nicola Sturgeon will announce the latest review of lockdown rules north of the border.
Ms Sturgeon had already warned her latest review was “likely to take a very cautious approach”.