Prime Minister Boris Johnson has promised to keep the two-metre social-distancing restriction, which is currently in place for all nations in the UK, under “constant review”.

But there have been calls from industry leaders and MPs to halve the distance to help businesses such as pubs and restaurants reopen, and allow more children to return to school.

Here the PA news agency presents the key points of the debate:

– Why has the UK been following a two-metre social-distancing rule while other countries have favoured a one-metre restriction?

Some countries, including France, Denmark and Singapore, have been following a distancing restriction half the measure of the UK limit.

This is because the World Health Organisation (WHO) recommended a “minimum” distance of one metre between people from different households to avoid transmission of the virus.

On June 1, researchers writing in the Lancet medical journal also endorsed a distance of “one metre or more,” adding that “distances of two metres could be more effective”.

– What is the science behind the one-metre minimum?

When someone coughs, sneezes or speaks they can spray small liquid droplets from their nose or mouth, which may contain the virus.

Jonathan Reid, a professor of physical chemistry at the University of Bristol, said large droplets can travel through the air a distance of one metre, whereas smaller droplets – around the diameter of a human hair – can travel two metres.

Prof Reid said: “It is just a matter of reducing risk with increased physical distance.

“The further you stand away from someone, the fewer droplets you will be exposed to when someone sneezes or coughs in your direction.”

– Why is the two-metre distancing rule now under review?

Boris Johnson said he is considering reducing the two-metre social-distancing restriction to allow schools in England to reopen fully by September.

Although primary schools were encouraged to open to more pupils from June 1, many school leaders said they were not able to because of a lack of space for distancing.

From Monday, shops, zoos, and theme parks in England will also be able to open their doors, but many businesses have warned that the two-metre rule would jeopardise their ability to reopen too.

– What have key politicians said?

Some Tory MPs, including former cabinet ministers Sir Iain Duncan Smith and Damian Green, have urged the Government to reduce the two-metre rule on the basis it is essential for the economy.

Business Secretary Alok Sharma has said the restriction is being kept under review, and would be amended “when it is safe to do so”.

He told the Commons on Tuesday: “We are taking a cautious view on this. I completely understand why for economic reasons businesses will want to have a look at this two-metre rule.”

Northern Ireland’s economy minister Diane Dodds said on Thursday that reducing the limit from two metres to one would give restaurants “a decent chance of survival”.

– How could retail workers benefit from a reconsideration of the two-metre guideline?

Those working in the hospitality industry have said a reduction to one metre would save thousands of jobs.

With two metres, restaurants would be running at about 30% of their full capacity, according to Mrs Dodds.

At one metre it would be 75 or 80%, the minister said.

– How would reducing the distance limit help schoolchildren and their parents?

The Department for Education (DfE) figures show that 52% of education settings that normally have children in nursery, Reception, Year 1 or Year 6 were open to at least one of these year groups in the first week they were able to go back.

Since many schools have cited the two-metre rule as a reason for remaining closed to most pupils, a lifting of this restriction would enable more children to return to their education.

This would also allow parents to return to work, especially those who cannot afford childcare.

Chief executive of single parents’ charity Gingerbread, Victoria Benson, has highlighted this is a major concern for sole parents being asked to return to work in the coming weeks.

– What do the public think?

According to a recent YouGov poll, 58% of people think social distancing should be kept at two metres.

Some 24% argued the distance should be one metre, and 8% said social distancing should be scrapped altogether.

The survey of more than 3,500 Britons on June 11 also showed that people aged over 65 are more likely to favour a change from two metres to one metre, with younger people erring on the side of caution.