Public Health England (PHE) said 73 cases of the B.1.617 variant have been confirmed in England as well as four cases in Scotland.
Officials consider it a “variant under investigation (VUI)” rather than a “variant of concern” (VOC), which includes the Manaus, UK and South African variants.
Why are there concerns about the Indian coronavirus variant?
The Indian coronavirus variant is considered to have concerning epidemiological, immunological or pathogenic properties.
Paul Hunter, professor in medicine at the University of East Anglia, said the variant features two "escape mutations" – E484Q and L452R – which "are causing people to be concerned".
"There's laboratory evidence that both of these are escape mutations," he told the PA news agency.
"Basically, applying what we know about other human coronaviruses would suggest that this is going to be even less controlled by vaccine. But we don't know that for certain at the moment."
This variant, along with others, has demonstrated the way in which Sars-CoV-2 can adapt to a human host when placed under selective pressures.
Their unique mutations are specific to the three-dimensional spikes that coat the shell of the virus. “If you think of a lock and key mechanism, the spike protein is the key and then the lock is the receptor on a human cell,” said Professor Deenan Pillay, a virologist atUniversity College London.
Through evolution, this structure has changed shape to make it easier for the virus to bind with and penetrate our cells, as seen with the UK variant.
In some cases, as with the South Africa and India variant, it has mutated to become less recognisable to neutralising human antibodies which would normally attach to the virus’s spike protein and block its entry.
This type of mutation therefore allows Sars-CoV-2 to slip past the first line of immunological defence in people who have been vaccinated or previously infected, enabling the virus to carry on circulating.
Dr Jeffrey Barrett, director of the Covid-19 Genomics Initiative at the Wellcome Sanger Institute, said that B.1.617 should be "watched carefully" but it is "probably not at the top tier of mutations that generate the most concern".
He told BBC Radio 4's Today programme that the first cases of the variant were identified late last year.
"This variant has a couple of mutations that are among those that we think are important that should be watched carefully, but they're actually probably not at the very kind of top tier of mutations, for example in the B117 – or Kent variant – or the South African variant, that generate the most concern.
"And in terms of spread, clearly this variant has increased in frequency in India around the same time as their very large and tragic recent wave.
"But I just don't think we know yet whether there's a cause-and-effect relationship – is this variant driving that spread? Or is it happening at the same time perhaps due to a coincidence?"
Will the UK ban travel from India?
Covid-19 rates are soaring in India, with more than 13.9 million confirmed cases and 172,000 deaths.
However, the country is not currently on the UK government’s “red list” of travel ban nations.
British or Irish nationals, or people with UK residency rights, are able to return from red list countries but must isolate in a quarantine hotel for 10 days.
Boris Johnson has meanwhile cancelled his visit to Delhi next week as a result of the deteriorating situation in India.
The Prime Minister's already-curtailed trip was scrapped altogether on Monday, with plans for him to instead speak to his Indian counterpart Narendra Modi later in the month.
Downing Street issued a joint statement from the British and Indian governments.
"In the light of the current coronavirus situation, Prime Minister Boris Johnson will not be able to travel to India next week," the statement said.
How did the variant arrive in the UK?
Prof Hunter said it is "not surprising" that the variant has come from India.
"If you think about where the main variants have arisen – South Africa, the UK, California, Brazil, and now India – all of these are countries that have really struggled to keep case numbers down,” he said.
"So it's not surprising. India has got a huge pandemic, and therefore that's where you're going to be getting the variant."
He added: "The big, big anxiety with this one is that it seems – and again this is still a little bit speculative because it hasn't been confirmed – but... there are two mutations here that are causing people to be concerned."
How many variants does the UK have?
There are now seven VUIs and four VOCs being tracked by scientists in the UK.
A significant cluster of cases of the South African variant of the virus were found in the London borough of Wandsworth, Lambeth, Barnet and Southwark earlier this week.
A total of 600 cases of the variant of concern have been detected so far in the UK, an increase of 56 in a week.
It prompted a large-scale surge testing operation to test thousands of people living and working in those areas.