Pushing ahead with a full reopening later this month in England would be “foolish” and a “major risk”, an expert has warned amid reports a two-week delay to the planned easing of restrictions is being considered.

There is currently enough evidence to say that due to the spread of the Indian variant one of the Government’s four key tests for its road map out of lockdown has not been met, Professor Stephen Reicher said.

Multiple reports have suggested plans to lift all restrictions on June 21 could be scaled down, with social distancing and the wearing of face coverings set to continue amid concerns that the variant that originated in India, now known as Delta, is fuelling a surge in cases.

On Friday the UK recorded its highest number of new confirmed coronavirus cases – 6,238 – since late March, according to official figures.

Saturday’s figure was down slightly at 5,765 lab-confirmed cases.

Meanwhile figures from the Office for National Statistics (ONS) suggested the number of people who had the virus in England has increased by around three-quarters in a week, taking it to its highest tally since mid-April, with the R value between 1 and 1.2.

Prof Reicher, a member of the Scientific Pandemic Insights Group on Behaviours (Spi-B) which advises the Government, said the criteria about the current assessment of the risks not being fundamentally changed by new variants of concern is “not upheld”.

He told the PA news agency: “I think by the Government’s own criteria it’s quite clear that it would be foolish to proceed on the data that we’ve got at the moment. The risk would be very great indeed.

It is about data not dates, and if you make it too much about the dates then you box yourself into a corner and I think that’s what the Government has done

“And of course it’s a balance of risks but I think it would be a major risk to go further in opening up.”

He added: “Again, I make the point that it is about data not dates, and if you make it too much about the dates then you box yourself into a corner and I think that’s what the Government has done.”

A UK Government spokeswoman said “no decision” had been made on whether to ease all coronavirus restrictions on June 21, amid reports Boris Johnson could delay the move by at least a fortnight.

“As the Prime Minister has set out, we can see nothing in the data at the moment to suggest that we need to deviate from the roadmap,” said the spokeswoman.

“We continue to look at the data and the latest scientific evidence and no decision on Step 4 has yet been made.”

Professor Reicher’s comments come as more surge testing is to be rolled out in another part of the country amid community spread of the Delta variant, with everyone aged 12 and above in some postcodes in Reading and Wokingham offered PCR testing from Monday.

Meradin Peachey, director of public health for Berkshire West said cases are mainly among young people, with “virtually nobody over 60 or anyone who has been vaccinated”.

She told BBC Breakfast: “If the variant spreads and becomes even more, it may mutate again and the big concern is that vaccines won’t work and that’s my big concern.”

Dr Mike Tildesley, a member of the Scientific Pandemic Influenza Group on Modelling (Spi-M) Government advisory panel, said the Government has a “difficult call” to make about easing restrictions on June 21.

He told Times Radio: “The difficult situation the Government have is of course if you delay that then of course you’ll get a smaller subsequent wave.”

But he added: “Of course, if you delay that we know that negatively impacts businesses, people’s livelihoods, and so forth.”

Hospitality chiefs have already voiced concerns over a delay to restrictions being lifted, saying it could threaten the viability of the sector.

Sacha Lord, night time economy adviser for Greater Manchester, branded June 21 a “make or break” date for many and vowed that he was “up for a fight” over the possible shift in timeline.

According to the Telegraph, a two-week delay to the final stage of Boris Johnson’s road map will be used to accelerate second jabs for over-40s, moving from a 12 to eight-week gap between doses, echoing the practise that is already in place for over-50s.

Those aged over 25 will also be offered their first doses from next week, the newspaper said.

It comes as laboratory data from the Francis Crick Institute backed up a policy of reducing the gap between jabs.

The study found that after just one dose of the Pfizer jab, people are less likely to develop antibody levels against the Indian (B.1.617.2) variant as high as those seen against the previously dominant Kent variant, which has been dubbed Alpha.

Dr Rosalind Eggo, also a member Spi-M, said with “very early evidence” showing that the current vaccines on offer “don’t work quite as well against the Delta variant”, it was important to increase the rate of second jabs.

“Getting those second doses up, pushing that number up as high as possible is really important,” she told BBC’s Newsnight.

Professor Anthony Harnden, deputy chairman of the Joint Committee on Vaccination (JCVI) said no decision on reducing the gap between doses for the over 40s had been taken but was likely to be made “in the next few weeks”.

He said cutting the gap from 12 weeks to eight is a “trade-off between better short-term protection and better longer-term protection”.

He told BBC Breakfast: “We will look at vaccine supply in the under-50s and make a decision about whether we should bring that forward, based on the prevalence of the variant which is circulating at the moment.”

More than 40 million people across the UK have received a first vaccine, with Government figures showing that of the 67,284,864 jabs given in the UK up to June 4, 40,124,229 were first doses.

NHS national medical director Professor Stephen Powis said the “latest milestone” in the fight against the pandemic “gives us another welcome opportunity to thank everyone in the NHS working flat out to deliver the biggest vaccination programme in our history”.

The i newspaper said revised plans to the road map would be likely to see the Government backtrack on encouraging a return to the workplace and continue with the guidance to work from home if possible, and could also see the policy of mask wearing and social distancing on public transport continue.

The newspaper also said social distancing in bars and restaurants is likely to remain, along with limits on audiences in theatres and cinemas.

In Wales, First Minister Mark Drakeford has confirmed he is considering keeping social-distancing restrictions in place for the rest of 2021, calling the two-metre measure “one of the strongest defences that we have” against the virus.

Kate Nicholls, chief executive of UKHospitality, said keeping social distancing would mean “June 21 is not freedom date at all”

She tweeted: “It means that those businesses continue to operate at a loss and threatens the long term viability of businesses, jobs and the recovery.”

Analysis by the PA news agency shows the majority of major hospital trusts in England are currently continuing to average no Covid-19 admissions despite rising case numbers, with 50% of the population now fully-vaccinated.