Mr Whitty said his assessment was based on the rising rate of Covid infections in the south east of England. In a statement, England’s chief medical officer said: “As announced on Monday, the UK has identified a new variant of Covid-19 through Public Health England’s genomic surveillance.
“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.”
Boris Johnson will hold a news conference on Saturday afternoon as Covid cases continue to rise.
The Prime Minister will be joined by Prof Whitty and Sir Patrick Vallance, England’s chief scientific adviser.
Mr Johnson has also scheduled a lunch time phone conference with his Cabinet ministers to discuss the crisis.
The Prime Minister’s news briefing will come after he refused to rule out a third national lockdown after Christmas.
Speaking on Friday he said he hoped England would not need to go into another shutdown after the rules on household mixing are temporarily relaxed for five days over the festive season.
Arlene Foster, First Minister of Northern Ireland, said she was “very concerned” about the new strain of Covid.
She tweeted: “Just finished a call with the other UK First Ministers & CDL Michael Gove about how the UK handles this new strain of Covid prevalent in SE England. Very concerning.
“Important we all follow the regulations so we keep virus under control in Northern Ireland.”
Scotland’s First Minister Nicola Sturgeon warned “preventative action may be necessary” to stop the spread of the new strain of the virus north of the border.
She wrote on Twitter: “Following a 4 nations COVID call earlier, I’ll chair @scotgov Cabinet meeting this afternoon to discuss emerging evidence on new variant.
“Cases currently at lower level in Scotland than UK – but preventative action may be necessary to stop faster spreading strain taking hold.”
This is a breaking news story… More to follow…