Boris Johnson is being "over-cautious" in keeping all schools closed until March 8 because there "really isn't a case" for refusing to open them earlier, some of the Government's own scientific advisers have said.
The success of the vaccination programme means there is no longer any risk of an "explosive third wave" if primary schools start to reopen after half-term, they argue.
Separately, MPs have been told by scientists that it is already safe to open classrooms in some parts of the country after the seven-day infection rate fell to its lowest level since mid-December.
However, Downing Street has insisted it will only be safe to begin opening schools from March 8, when the over-70s will have built up immunity through vaccines.
New modelling suggests the 'R rate' of the virus is at its lowest point since last April and well below the all-important figure of one, suggesting the vaccination programme is causing Covid to retreat.
Almost 11 million jabs have now been administered, with more than three million people vaccinated in the past week, putting the NHS well on course for the target of offering vaccines to all over-70s by February 15.
Another 20,634 positive tests were reported on Thursday, together with 915 deaths, but the trend in cases, deaths and hospitalisations continues to fall. The infection rate per 100,000 people is now 61 per cent lower than at the start of the third lockdown a month ago.
Scientific opinion on whether it is safe to reopen schools is divided, with some Government advisers claiming even March 8 might be too early. However, several others have now broken rank to say the latest evidence shows it would be safe to begin the reopening of schools on February 22 after the half-term break.
Professor Robert Dingwall, a member of the New and Emerging Respiratory Virus Threats Advisory Group (Nervtag) committee, told The Telegraph that, by the end of February, around one third of the population will have high immunity through vaccinations or previous infections, meaning reopening schools is now "a political calculation more than a scientific one".
He said that around 90 per cent of those most at risk of dying will have been protected and intensive care admissions for Covid-19 are likely to have gone down by up to 30 per cent by then.
Speaking in a personal capacity, he said: "Many people looking at this think it's a tolerable risk to get the kids back as the Scots are doing. We could start getting primary school children back after half term, and there really isn't a case for keeping all kids off until March 8.
"The Scottish advisers tend to be more conservative than the English ones, so it's very hard to resist the conclusion that the English are being a little over-cautious this time. If you have the first three years of primary coming back immediately after half term that is not now going to create an explosive third wave."
Scientists at University College London believe the 'R' rate as of Tuesday was 0.65 to 0.86, considerably better than the official government estimate published last Friday of 0.7 to 1.1.
A member of the Scientific Pandemic Influenza Group on Modelling (SPI-M) which advises the Government, said there was now room to reopen schools even if it pushed up the 'R' number slightly.
Speaking in a personal capacity, Mark Woolhouse, professor of infectious disease epidemiology at the University of Edinburgh, said: "The latest Sage data on the contribution of reopening schools on the 'R' number is between 0.2 and 0.5.
"That's a huge range, and my reading of the evidence is that it is at the lower end, which would suggest that you could reopen primary schools after the February half term.
"When the Prime Minister announced the March 8 date, he said schools were being kept shut to prevent a surge in cases. But there's never been a surge in cases when schools have reopened, not just in the UK but across Europe. Reopening schools is not immediately going to create large numbers of people in hospitals."
Muge Cevik, a clinical lecturer in infectious diseases at the University of St Andrews and a member of Nervtag, told a teleconference on Covid-19 and schools last week that studies carried out abroad had shown no increase in hospitalisations and deaths following schools reopening.
Other Government advisers, however, have warned that cases will rise again when schools reopen and that case numbers need to come down further before that can be considered.
On Thursday, The Telegraph disclosed that Rishi Sunak, the Chancellor, has told allies he fears scientists are "moving the goalposts" by changing the targets they say need to be met before lockdown can be eased.
The Telegraph has found that at least four other Cabinet ministers share his view, with one source saying: "Several Cabinet ministers are worried about the scientists trying to push back on the promises the PM has already made. How can anyone plan if once a target is met, another one is suddenly set?"
One member of the Cabinet said: "There are Cabinet ministers who agree with him."
Increasing numbers of Tory MPs have publicly called for schools to be opened before March 8, and Jacob Rees-Mogg, the Leader of the Commons, said children struggling with mental health could attend school.
He said: "Schools have the flexibility to offer a place in school to vulnerable children, which might include those for whom being in school helps them manage their mental health."
Earlier this week, Professor Anthony Costello, a former director of the World Health Organisation, suggested schools could reopen once case rates were down to 100 in every 100,000 people.
He told the All-Party Parliamentary Group on coronavirus that Professor Karl Friston, a neuroscientist at University College London, had quantified the "safe" level at that figure, meaning some areas could open schools now. Among the areas with fewer than 100 cases per 100,000 people are Devon, north-east Lincolnshire, Swansea and Edinburgh.
A senior Government source said: "The reason the date has been set at March 8 is because that will be three weeks after the first cohort of people have been vaccinated and developed a high level of immunity. The Government's view is also that we are still waiting on data to show the extent of the impact of the vaccines."
Paul Hunter, professor of medicine at the University of East Anglia, said he believed people would be able to meet up with friends and family from next month, telling BBC Radio 4's World At One: "Personally I believe we should be able to start doing that probably not long after [schools reopen] - if I had to bet on a time, I'd say some time in March certainly."