The government's SAGE committee says the R rate is between 1.1 and 1.4 across the UK.
The Scientific Advisory Group for Emergencies (SAGE) says there is "widespread growth of the epidemic across the country" with infections growing by up to seven per cent a day.
The ONS says that in the first week of September there were 6,000 news cases of coronavirus every day - and that is doubling week on week.
The R number from above 1 last week for the first time since early March and could now be as high as 1.4 - basically that means each person who has coronavirus infects 1.4 people.
That could mean the UK's coronavirus alert level is raised back to 4 (A COVID-19 epidemic is in general circulation; transmission is high or rising exponentially) from the current level of three.
It was lowered in June.
Yvonne Doyle, medical director at Public Health England, said: "We're seeing clear signs this virus is now spreading widely across all age groups and I am particularly worried by the increase in rates of admission to hospital and intensive care among older people."
"This could be a warning of far worse things to come," she said.
