The Prime Minister is holding emergency talks with Cabinet ministers this afternoon.
The move comes amid reports that the Mr Johnson could order new travel restrictions for the south east in an attempt to stop it spreading to the rest of the country.
It comes after scientists confirmed that the new variant coronavirus found was spreading more rapidly.
Professor Chris Whitty, chief medical officer for England, said the UK has informed the World Health Organisation about the strain.
‘As announced on Monday, the UK has identified a new variant of Covid-19 through Public Health England’s genomic surveillance,’ he said in a statement.
‘As a result of the rapid spread of the new variant, preliminary modelling data and rapidly rising incidence rates in the South East, the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) now consider that the new strain can spread more quickly.
‘We have alerted the World Health Organisation and are continuing to analyse the available data to improve our understanding.
‘There is no current evidence to suggest the new strain causes a higher mortality rate or that it affects vaccines and treatments, although urgent work is under way to confirm this.
‘Given this latest development, it is now more vital than ever that the public continue to take action in their area to reduce transmission.’
The Prime Minister will hold a press conference later with the chief medical officer Chris Whitty and the chief scientific adviser Sir Patrick Vallance, Downing Street has said.