Dr Susan Hopkins, of Public Health England, said every region in the UK has cases of the new variant, though in very small numbers.
“It has been detected in many other parts of the country”, she told Sky’s Sophy Ridge On Sunday. “Every region has cases but with very small numbers.
“It has also been detected in Wales, in Scotland, we have not had any detected in Northern Ireland.”
Her comments come after Prime Minister Boris Johnson put London and the South East under tight restrictions from Sunday, effectively cancelling Christmas for almost 18 million people.
Watch: What is the new COVID variant?
Announcing the new restrictions - and the change to the relaxation of coronavirus rules from five days over Christmas to Christmas Day only - Johnson revealed that scientists on the Government’s New and Emerging Respiratory Virus Threats Advisory Group (Nervtag) is spreading more quickly.
Dr Hopkins said while the new strain had been identified in October from a sample taken in September, it was not until Friday that its higher transmissibility was confirmed.
Asked why the Prime Minister was still insisting on Wednesday that it would be “inhuman” to cancel Christmas, she said: “We did not have the modelling evidence to show that the transmissibility was increased or that the R value was increased on Wednesday.”
Dr Hopkins also urged people who had crammed onto trains out of London after Saturday’s announcement to reduce their contacts to minimise the risk of transmission to other parts of the country.
She said: “I understand people’s wish to get home to their families and loved ones that they may live with on a normal day-to-day basis and wanted to get out of London last night.
“I hope that when they go to wherever they are moving to they reduce their social contacts and don’t contact anyone outside their household for the next 10 days, as that will help minimise the risk of transmission to other parts of the country.
“We know it’s in other parts of the country in small amounts but what we are trying to do is prevent more spread and rapid increases across the rest of the country.”
Watch: What is long COVID?