Lab results in the two weeks through May 15 suggest that more than 85% of community cases in these areas were the Indian variant – up from 28.6% in the two weeks through April 24 in Bolton and 18 % in Blackburn. with Darwen.

In total, Bolton saw 1,153 confirmed cases of the Indian variant, while Blackburn with Darwen saw 318.

Bedford in eastern England and Sefton in Merseyside have become two other hot spots for the strain, with local authorities seeing more than 80% of cases detected as an Indian variant through May 15.

Likewise, Croydon, Chorley, Nottingham and Hounslow all saw at least 70% of the cases detected as a variant during the same period.

During a recent Downing Street coronavirus briefing, Boris Johnson said there were “significant unknowns” about the Indian variant, including the extent to which it is more transmissible than previous strains, which could in turn mean delaying the final stage of lifting the lockdown in England.

However, the prime minister stressed that there is no evidence that the vaccines will be less effective, saying: “We are in a different position from the last time we faced a new variant, before Christmas.”

The first real data released on Saturday showed that the double doses of Pfizer / BioNTech or AstraZeneca jabs were “very effective” against the Indian variant, giving hope that the UK will be able to fully reopen on June 21.

NHS officials have started drawing up plans that speed up the vaccine rollout schedule, amid concerns about the spread of the Indian variant among young adults.

The vaccine rollout could reach young people in their twenties during the first weeks of June, The telegraph understands, with the hope that all over 18s could be offered jabs by the end of the month.

The government is also speeding up second doses for those over 50 and those at risk to just eight weeks, and will send additional vaccines to areas where clusters of the Indian variant are found.