BORIS Johnson has insisted the easing of lockdown restrictions has to be based on a “cautious and prudent approach” as an expert told MPs that unlocking must be driven by “data not dates”.

The Prime Minister’s remarks came as reports suggested the UK Government was planning a “surge-testing” blitz in England with 400,000 30-minute lateral flow tests sent to homes and workplaces every week in a bid to keep on top of any future rise in Covid-19 infections.

It was in the autumn when Matt Hancock, the UK Government’s Health Secretary, promoted the idea of a so-called “Operation Moonshot” mass testing programme to enable sport venues and theatres to test people before allowing them in. His contribution, however, sparked laughter from the Labour benches in the Commons chamber.

Dominic Raab, the Foreign Secretary, said UK ministers had “ambitious targets” when asked about the 400,000 weekly lateral flow tests, noting how testing pilots such as in Liverpool had shown “value” of testing carried out at scale.

On Monday, Mr Johnson is expected to flesh out details of his plan for a mass testing regime when he makes public his road-map to easing lockdown restrictions south of the border. A Commons statement is expected as is a Downing St press conference later in the afternoon.

Speaking at a mass vaccination centre in Cwmbran, south Wales, the PM was asked if he agreed with comments made by Professor Dame Angela McLean, the Chief Scientific Adviser to the Ministry of Defence, at the Commons Science and Technology Committee this morning, that any unlocking should be based on “data, not dates”.

Mr Johnson replied: “I do think that’s absolutely right. That’s why we’ll be setting out what we can on Monday about the way ahead and it’ll be based firmly on a cautious and prudent approach to coming out of lockdown in such a way to be irreversible.

“We want to be going one way from now on, based on the incredible vaccination rollout that you’re seeing in Cwmbran.”

The PM hailed the “outstanding” vaccination rollout across the UK and expressed his hope that it was driving down coronavirus infection rates.

"One of the big questions people will want to ask is to what extent now is that being driven by vaccination. We hope it is, there are some encouraging signs, but it’s still early days,” he added.

Earlier, Dame Angela told MPs: “Things are all moving in the right direction; infections are falling, the number of cases are falling, hospitalisations and deaths. But we still stand with a high number of infections.

“There were about 20,000 people in hospital earlier this week. By comparison, in early May there were about 15,000 patients but there’s still a lot of people in hospital.

“I share everybody’s optimism about how fantastic this vaccine is. But I would say we need to be optimistic and cautious, there’s still a lot of infected people out there.”

When asked if the R level needed to be at a certain level before lockdown could be eased, Dame Angela said: “The timing is probably more important, it’s how many of the people who are more at risk – that’s a mixture of old people or people with underlying conditions – have been vaccinated before we do more unlocking.

“The important issue is to really watch very closely what is happening, so that if infections start to increase and that we do everything we can to decide whether it is a good moment to take another step in unlocking. Let’s use data, not dates.”

Asked about the easing of the first lockdown last spring, Dame Angela replied: “Caution was our friend; we did actually ease it pretty slowly and I would say things went very well.

“From May to September, I would give a big tick and say that was well managed. In November, we were hit with that new variant and, with hindsight, we came out of the November lockdown too early.”

Mark Woolhouse, Professor of Infectious Disease Epidemiology at the University of Edinburgh, said he would not expect a surge in cases when schools reopened; some are due to do so in Scotland from Monday with others in England set to return in March.

“One of the stated reasons for keeping schools closed was to avoid some surge in cases when they open; that’s never happened across western Europe,” declared Prof Woolhouse.

“There was a different prediction when the universities went back; there a surge in cases was expected and we saw a surge in cases.

“We know what a surge in cases looks like; we saw it in September and October in the universities, we’ve never seen that in the schools, and I don’t expect to,” he explained.

The expert stressed how a distinction had to be made although, he pointed out, there was an issue about the oldest children who were more adult-like in the biology of the virus infection within them.

“So, what other countries in Europe have done – Sweden is a good example – is to keep their schools open to children up to 15 years old. Older children are more of a challenge but, for many of the children, the contribution that they’re making to the cause of this epidemic has been proven by the data not to be that great.”

Prof Woolhouse argued that schools did not appear to drive the epidemic but, rather, “reflect the epidemic around them”.

Noting how children were at “very low risk” from catching the virus and evidence pointed to school staff not being at an elevated risk compared to other working professionals, the academic explained how the discussion was all about the contribution schools made to the infection rate generally, the R number.

“There is a case, certainly for children under 16 up to 15, that having them in school does not make such a big contribution to the R number that we couldn’t consider lifting it in the reasonably near future.

“I completely agree that we don’t want to be overly focused on dates, not at all. We want to be focused on data. But the point I’d make about that is the data are going really well.

“The vaccination rollout is exceeding most people’s expectations, it’s going very well.”

Prof Woolhouse added: “The transmission blocking potential is key. But so, of course, is its actual ability to protect against death and disease, and to keep people out of hospital, and those numbers are looking really good.

“My conclusion from that is if you’re driven by the data and not by dates, right now, you should be looking at earlier unlocking.”

Earlier, however, NHS Providers Chief Executive Chris Hopson warned the number of C19 cases needed to plummet to under 50,000 before the PM should consider easing lockdown measures south of border. The latest figure is 695,400. Mr Hopson points out how there were 500 Covid patients in hospital in September but 15 weeks later there were 34,000.

Meanwhile, the world’s first coronavirus human challenge study will begin in the UK within a month, following approval from the UK’s clinical trials ethics body. It will involve up to 90 carefully selected, healthy adult volunteers being exposed to Covid-19 in a safe and controlled environment. The study aims to establish the smallest amount of virus needed to cause infection.