The Indian variant may not be as transmissible as first feared, with the recent surge in cases partly driven by the "founder effect", scientists have said.
Fears that the mutated virus could be 40 to 50 per cent more infectious have led some in the UK to claim the British government should not have carried on with releasing restrictions this week.
Yet cases in India are declining rapidly, leading some experts to think that the variant may not be as dangerous as first thought.
Some argue that the recent spike is being driven by the founder effect, which occurs when a small number of people infect a larger number than normal, sparking a change in the dominant strain.
In Britain's case, the effect may have been triggered by small numbers of infected people racing to return from India after the government imposed new travel restrictions, and then passing it on to large, multi-generational households.
The effect is likely to be exacerbated by case numbers currently being so low in Britain, allowing the variant to easily take over from the Kent variant, despite no more increased transmissibility.
Prof Carl Heneghan, director of the Centre for Evidence-Based Medicine at the University of Oxford, said: "How can it be the case that it is 40 per cent more transmissible when the numbers are falling off at the speed they are in India?
"We could be looking at a founder effect and where you've got a small number of people having a bigger impact.
"India is actually looking more like the natural curve which happens in winter and has a high drop-off, as opposed to flattening the curve."
At a press conference from Downing Street on Wednesday evening (local time), Professor Jonathan Van-Tam, the Deputy Chief Medical Officer, said that the extra transmissibility could be as low as "just a few per cent" and was expecting the data to firm up next week.
"We have a credible range which goes from a few per cent through to 50 per cent more transmissible," he said.
"I think most people feel it's going to be in the middle but it is just too early."
Prof Van-Tam warned that the transmission was not inevitable if those in hot spots exercised caution.
"The government has given the public freedoms to start to make them for them," he added.
"We can't live for years and years on end with rules, people will have to learn to manage these risks from Covid for themselves because this is not going to go away."
Prof Neil Ferguson, of Imperial College, said latest figures show that the initial spike was slowing. Cases in Blackburn have now started to plateau, and the curve in Bolton also appears to be growing shallower.
"The challenge we have ... it was introduced overseas, principally into people of Indian ethnicity, often living in multi-generational households, often in quite deprived areas with high density housing," Prof Ferguson told the BBC.
"We are trying to work out whether the rapid growth we have seen in Bolton is going to be typical of what we could expect elsewhere or whether it is something known as a founder effect, which is often seen in these circumstances.
"There's a glimmer of hope from the recent data that while the virus is there it does appear to have a significant growth advantage, the magnitude of that advantage seems to have dropped a lot with the most recent data.
"The curves are flattening a little but it will take us a little longer to be definitive about that."
Data also show that Indian variant is largely circulating in unvaccinated groups and there is no evidence it is causing a rise in hospital admissions or deaths.
Prof John Edmunds, of the London School of Hygiene and Tropical Medicine, said that it appeared the vaccine rollout was combating the variant, even if it did turn out to be more transmissible.
On Wednesday, Boris Johnson said there was growing evidence that the vaccines were still working against the Indian variant, and thanked people in Bolton and Blackburn for coming forward in record numbers to receive the jab.
The Prime Minister told MPs on Wednesday: "We've looked at the data again this morning and I can tell the House we have increasing confidence that vaccines are effective against all variants, including the Indian variant."
Experts said it was important to carry on with the roadmap cautiously.
Dr Mike Tildesley, associate professor at the University of Warwick, said: "The relaxations on May 17 are extremely important for people's mental health and well being after a lengthy period with severe restrictions in place, but the emergence of the new Indian variant serves as a reminder that we need to continue to ease carefully out of lockdown and continue with the vaccination campaign in order to minimise the risk of a resurgence occurring over the coming weeks."