The two-metre rule could be relaxed in Britain to allow more pubs and restaurants to reopen this summer, officials have suggested.
Public Health England is assessing the strict distance rule which could offer hope to beleaguered landlords and business owners.
Ministers are considering allowing some pubs and restaurant to reopen beer gardens and outdoor spaces from July.
Pubs have warned a strict two-metre rule would be unworkable for those without large beer gardens and make reopening impossible for most.
PHE’s health protection director Prof Yvonne Doyle told MPs: “This will be the subject of continued investigation whether two metres is actually necessary or whether that can be reduced.
“It’s quite right we can review and learn from that. I’m sure that’s right.”
“It’s an important decision and we are fully aware of that,” she added.
MPs on the Science and Technology Committee called the two-metre PHE guidance a “gross over-simplification”.
Many other countries follow World Health Organisation guidance that one metre can be safe enough when other safeguards are in place.
One option could be to allow punters to be one metres apart in areas where they will not stay in one place for long.
A leading expert in building engineering and airborne infections said most Covid-19 infections are spread via contaminated surfaces rather than particles in the air.
Prof Catherine Noakes serves on the Scientific Advisory Group for Emergencies (SAGE) informing Government lockdown measures.
She told MPs: “If you are a metre or two metres away from someone you can still get that face-to-face transmission, but further away the outdoor environment disperses it.
“The chances of you being able to inhale enough outdoor is very very small.”
Prof Noakes referenced a Chinese study of 7,000 infections which found all but one were transmitted indoors.
PHE admitted the decision was a “trade off” between the economy and concerns of the public about a second wave of infections.
Prof Doyle said: “It’s a learning experience internationally and we are aware of the international differences.
“We have looked at a range of international evidence and the WHO advises two metres [when in contact] for 15 minutes.
“We have taken a precautionary approach to say two metres, particularly indoors.
“That is where we are at the moment but we are still learning about this virus.”
She added: “I know other countries use slightly less than that but until we know more the two metre distance is important.”
The science committee chair pointed out Australia, Germany, the Netherlands and South Korea had a 1.5 metre rule, while Hong Kong, Singapore, China and France advised just one metre
Greg Clark MP said: “Looking at the international comparisons that I see, we are an outlier at the extreme end of the distance that is recommended.”
Prof Andrew Curran, Chief Scientific Adviser at Health and Safety Executive, said: “As we learn more I think we have to do things slightly differently.”
He added: “When yo are dealing with members of the public who don’t always act in the way you expect them to act, that can be the barrier.
“That’s where the science can inform what mitigation we can take.
Industry leaders want social distancing reduced from two metres to one when they fully reopen to keep more of the 47,000 UK pubs in business.
It is feared only 20% could reopen if the restriction remains.
Emma McClarkin, boss of the British Beer and Pub Association, said: “A one-metre rule would put the majority pubs back in play.”
Being in close proximity with an infected person for more than 15 minutes has been shown to drastically increase the risk of contamination.
