The Scientific Advisory Group for Emergencies (Sage) said the range reflects the situation three weeks ago, adding that the number of cases in care homes and hospitals may account for the figure.
ITV News Science Editor Tom Clarke explains we should not be too worried about the rise in the R number, as it's a recalculation on where we were before changes to the lockdown were made
Meanwhile, the statistics are in line with what would be expected with a decrease in community cases.
R measures how many people on average an infected person transmits Covid-19 to.
Any increase will limit the government's ability to ease lockdown rules, according to their own guidelines.
He added: “Everybody can play their part in keeping R below one and pushing R down.
“You can do that by following the social distancing rules, so if you do go outdoors, do it only with members of your household and keep two metres away from others who aren’t in your household.
“And those social distancing rules are incredibly clear, and they will help to keep us safe.”
England's Deputy Chief Medical Officer, Dr Jenny Harries, said it is important to keep the R reproduction rate below 1.
Dr Harries said: "There’s quite a range there, 0.7 to one, in the estimate of ‘R’ and this is for a number of reasons.
"Partly because a number of different models are used to model this data and it’s important that they challenge each other and that we get the consistency of that."
Sir Patrick Vallance, Government Chief Scientific Adviser said:“R is one of the important things you can track to understand an epidemic. If you can estimate R, then you have part of a reliable tool for planning how to combat the virus.
“If the R is higher than one that means this disease is growing exponentially and will keep on spreading to more and more people.
"To keep R below one and control the virus, it is vital that people stay alert and continue to follow the latest Government guidelines to the letter.
“In the coming weeks we will update this estimate regularly.”
Coronavirus: Everything you need to know: