Boris Johnson’s visit to India will go ahead despite soaring coronavirus cases and fears over a variant first identified there, according to Downing Street.

Public Health England (PHE) reported that 73 cases of the B.1.617 variant have been found in England, as well as four cases in Scotland, which an expert said could be a cause for concern.

Officials have currently designated it a “variant under investigation” (VUI) rather than a “variant of concern” (VOC), such as the Manaus (Brazil) or South African variants.

The Prime Minister had already scaled down his trip to India at the end of April due to the country’s worsening coronavirus situation, but Downing Street has insisted it will still go ahead.

A No 10 spokesman told a Westminster briefing: “The Prime Minister’s visit is still happening later this month.

“We have said that the programme will be slightly shorter than it will have been, and you can expect the main body of his programme to take place on Monday April 26.

“As you would expect, safety is obviously important and is a priority for us on this trip, which is why we will make sure that all elements of the visit are Covid-secure.”

Mr Johnson was due to spend four days in the south Asian country at the end of the month but, following talks with Narendra Modi’s administration, the “bulk” of the meetings could be fitted into one day.

Officials said there is currently no evidence to suggest that disease from the newly identified variant is more serious than previous ones, nor is there current evidence to suggest vaccines are less likely to work against it.

The figure of 77 cases comes from the latest update of PHE’s surveillance of the distribution of different variants across the UK, based on data up to April 7.

It is understood that the cases detected in England are dispersed across different parts of the country and many are linked to international travel, but investigations are under way.

India has got a huge pandemic, and therefore that's where you're going to be getting the variant

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”.

Officials said “all appropriate public health interventions will be undertaken, including enhanced contact tracing” after its detection, with PHE and international partners monitoring the situation “closely”.

Prof Hunter said: “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.

“So it’s not surprising. India has got a huge pandemic, and therefore that’s where you’re going to be getting the variant.”

In India, Covid-19 rates are soaring, with more than 13.9 million confirmed cases and 172,000 deaths.

The country is not currently on the Government’s “red list” for travel, which sees people who have been in those countries in the previous 10 days refused entry to the UK.

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.

Asked why India has not been put on the red list despite the soaring number of cases, Downing Street said the situation is “under constant review”.

A No 10 spokesman told reporters on Friday: “We add and remove countries based on the latest scientific data and public health advice from a range of world-leading experts.

“We keep it under constant review and we won’t hesitate to introduce tougher restrictions and add countries if we think it is necessary.”

But Labour said the blame for the Indian mutation making its way into Britain “rests squarely with the UK Government”.

Shadow home secretary Nick Thomas-Symonds said: “Ministers have been warned time and again that failing to introduce a comprehensive hotel quarantine policy would leave us exposed to variants of Covid.”

According to PHE, the variant “includes a number of mutations including E484Q, L452R, and P681R”.

PHE said that mutations at the 484 spike protein have been associated with the Manaus and South African variants.

The E484K mutation is reported to result in weaker neutralisation by antibodies in lab experiments, but the E484Q mutation is different and still subject to investigation.

Lab studies suggest the L452R mutation may reduce antibodies binding to the virus, particularly seen in combination with other mutations, PHE said.

Viruses by their nature mutate often, with more than 18,000 mutations discovered over the course of the Covid-19 pandemic, the overwhelming majority of which have no effect on the behaviour of the virus.

PHE’s latest findings mean there are now seven VUIs and four VOCs being tracked by scientists in the UK.

In London, extra testing facilities were launched this week to help limit the spread of the South African coronavirus variant following a cluster of cases being discovered.