B.1.525 has a mutation called E484K that may help the virus slip past some of the body’s immune system defences.
This mutation is also found in the Brazil and South African variants.
The variant has since also been found in Australia, Denmark, the US, Canada, France, Ghana, Jordan, Singapore, Finland, Belgium and Spain.
Experts are studying the new strain to understand its risks.
Some 15 million people, or 22 per cent of the UK population, have received their first shot or were offered one.
The figure includes most people in the government’s top four priority groups, including everyone over 75, frontline healthcare workers and nursing home staff.