A "mutation of concern" detected in the UK variant of coronavirus has been found in 32 cases across Liverpool.
This mutation, known as E484K, is already present in both South African and Brazilian coronavirus variants.
Eleven cases in the Bristol area have been identified as the variant that originally arose in Kent but is now showing the E484K mutation.
A cluster of 32 cases in Liverpool also have the same mutation but relate to the original strain of coronavirus that has been around since the start of the pandemic.
Laboratory studies have shown that antibodies - which are produced by the body to counteract infection - are less able to bind to a part of the virus known as the spike protein, in order to stop it from unlocking human cells to gain entry.
It was previously thought this mutation was not present in the UK variant, also known as B.1.1.7.
Scientists say it is quite common for viruses to mutate and, more often than not, these mutations are harmless.
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But sometimes "mutations of concern" - such as E484K - can emerge, which can make the virus more transmissible or pose a risk of re-infection.
Dr Jonathan Stoye, group leader, Retrovirus-Host Interactions Laboratory at The Francis Crick Institute, said: "This suggests that the UK variant is now independently acquiring the E484K change.
"From a virological standpoint, the appearance of new variants by mutation during replication cannot be considered surprising.
"Whether this change will provide significant growth advantages for the novel virus causing it to predominate remains to be seen."
Dr Julian Tang, honorary associate professor at the University of Leicester, described the finding as "a worrying development, though not entirely unexpected".
He said it is important that people follow lockdown rules and get new cases of coronavirus down to prevent opportunities for the virus to mutate further.
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A vaccine developed by Pfizer and BioNTech appears to be effective against the UK variant of coronavirus, according to two lab studies.
But experts from the University of Cambridge found that when E484K was introduced to the variant, "substantially higher levels of antibody were required" to neutralise the virus.
According to the scientists, their findings, which have not yet been peer-reviewed, suggest the Pfizer/BioNtech vaccine may be less effective when dealing with the E484K mutation.
