The number is up from last week’s estimate which was between 1.0 and 1.2.
R represents the average number of people each Covid-19 positive person goes on to infect.
When the figure is above 1, an outbreak can grow exponentially but when it is below 1, it means the epidemic is shrinking.
It comes as Public Health England (PHE) shared data on the spread of the Delta variant.
It found that of the 1,234 people who attended A&E in England, between February 1 and June 7, confirmed as having the Delta variant of coronavirus, 825 were unvaccinated.
A further 220 attended A&E after having received their first dose of the vaccine, and 83 after their second dose.
The number of Delta variant cases has risen from 12,431 to 42,323 in the latest seven-day period, an increase of 29,892 cases, PHE said.
As the number of people in the UK catching the Delta variant, previously known as the Indian variant, continues to rise - politicians and scientists are debating whether or not final restrictions should be eased on June 21.