Manchester was today crowned the Indian 'Delta' variant hotspot of the country by official data.
Public Health England figures revealed the Northern city has identified the most cases of the mutant strain — 7,032 infections — since it first arrived on Britain's shores in April.
It was followed by Bolton (6,059), which was a hotspot for the variant when it started to take off in the country, and Leeds (5,790), which has also seen a major spike in cases.
Official figures also showed the Indian variant is still behind almost every single Covid infection in the country.
Over the week to July 7, the latest available, PHE surveillance found 36,800 of 37,256 cases checked for mutant variants were the Indian strain.
The only other variants spotted were the previously dominant Kent 'Alpha' variant which sparked the second wave, 453 cases, and the mutant strain linked to travel to Nigeria, three cases.
But this does not mean other mutant strains have disappeared because high case numbers at more than 40,000 a day have left officials only able to screen a small number for mutant strains.
The South African 'Beta' variant, which sparked surge testing and makes vaccines slightly less effective, could still be circulating in the country alongside others. There are warnings France could be slapped on the 'red list' today because of surging cases of this variant.
The Indian Covid variant sparked Britain's third wave of the pandemic, and became the most common strain just two months after arriving on this country's shores in April.
It carries key mutations that scientists say make it the most transmissible variant to date, allowing it to rapidly take over from other types as it spreads between countries.
Boris Johnson faced warnings to delay allowing people to again dine indoors on May 17, when it became clear the strain was spreading rapidly. But the Prime Minister steamed ahead with easing restrictions because estimates suggested the strain would not lead to a rapid spike in hospitalisations.
By the end of May, the Indian mutation caused 77.7 per cent of cases across England, while the once-dominant Kent strain was responsible for just 21.8 per cent
The Indian 'Delta' variant is now dominant in more than 300 areas of England, MailOnline's analysis of testing data reveals. Figures show the ultra-transmissible strain had overtaken the formerly dominant Kent variant in 303 local authorities by June 12 — just two months after it was seeded in the country
The Indian variant is now responsible for almost all Covid cases in the country, with the most recent estimates from the Sanger Institute stating that 99.3 per cent of all cases in the two weeks up to July 3 were caused by the more infectious mutation
PHE checks a certain number of cases each week for mutant variants in order to keep track of which ones are already present in the country.
In May, when cases tumbled to 20,000 a week, they were able to check around half for variants.
But now as infections surge past more than 40,000 a day only a small proportion can be examined.
Variants carry different mutations on their spike proteins — used by the virus to invade cells — which make them either more infectious or better able to avoid vaccine-triggered immunity. These are detected by PHE and used to identify which variant an infection represents.
It comes after a Government minister warned today that Britain could face another lockdown if Covid rises to an 'unacceptable' level.
Solicitor General Lucy Frazer suggested it was the right time to open up because of the vaccination drive — which has reached 90 per cent of Britons.
But with cases continuing to soar, hospital admissions tracking above some of SAGE's worst-case projections, and deaths having hit a four-month high, she warned that No10 may be left with no choice but to consider reimposing tough restrictions.
Ms Frazer said: 'Of course, if we get into a situation where it is unacceptable and we do need to put back further restrictions, then that of course is something the Government will look at.'
England's chief medical officer last night cautioned the UK could still 'get into trouble again surprisingly fast' and hospitals may face 'scary numbers' within a matter of weeks.
Making it clear the country was not on an irreversible path to freedom despite No10 pushing ahead with step four of the roadmap to normality on Monday, Professor Chris Whitty said: 'We are not by any means out of the woods yet.'
Mr Johnson has already dropped all mention of the final unlocking being 'irreversible'. The Prime Minister has resorted to caution, calling on people not to 'go wild' and immediately rush to take advantage of the final easing — which includes lifting work-at-home orders and reopening nightclubs.
Cases have spiralled over the past few weeks, with scientists blaming the easing of restrictions and young men gathering to watch England's Euro 2020 campaign for the uptick.
Vaccines have already saved thousands of lives since the third wave began, drastically slashing the proportion of infected patients who are left seriously ill. But jabs aren't perfect, and admissions have been tracking upwards for a fortnight.
Almost 560 infected patients are being admitted to NHS wards each day now, compared to fewer than 100 before the Indian Delta variant took off in mid-May. The current trend in figures is above some of the gloomiest estimates from SAGE, who warned hospitalisations could breach 4,000 a day in August.
It comes after health chiefs yesterday posted another 63 deaths, in the highest daily rise since March, and 48,553 cases.
England's Covid hotspots where up to one in every 33 people are infected: Interactive map shows virus is most prevalent in Manchester as official data says cases jumped by 75% in a week across nation - with almost 580,000 people now carrying illness
By Joe Davies for MailOnline
One in 95 in England had Covid last week, official data revealed today amid warnings from ministers the country will face another lockdown if third wave doesn't stop spiralling soon.
Office for National Statistics (ONS) data — based on random swab testing of thousands of people — estimated the number of people infected with the virus in the week ending July 10 was 577,7000, up 73.5 per cent in a week.
Rates were highest in the North East of England, where up to one in 40 were thought to be infected, and among 18- to 24-year-olds, with up to one in 35 young adults carrying the virus.
Around 60,000 people in Scotland had the virus, while 8,400 people in Wales and 6,300 in Northern Northern Ireland were thought to be infected.
Meanwhile, SAGE today estimated England's R rate — which measures how quickly the outbreak is growing — is between 1.2 and 1.4, slightly down from last week's figure of between 1.2 and 1.5. It means, on average, every 10 people with the virus will infect between 12 and 14 other people.
The North East and Yorkshire and South East have the highest R rates — between 1.2 and 1.6 — while it is lowest in the North West, where it is between one and 1.3.
The figures come as a minister today warned the country would 'of course' face a new lockdown if infections hit 'unacceptable' levels.
Solicitor General Lucy Frazer suggested it was the right time to open up because of the vaccination drive — which has reached 90 per cent of Britons.
But with cases continuing to soar, hospital admissions tracking above some of SAGE's worst-case projections, and deaths having hit a four-month high, she warned that No10 may be left with no choice but to consider reimposing tough restrictions.
Cases have spiralled over the past few weeks, with scientists blaming the easing of restrictions and young men gathering to watch England's Euro 2020 campaign for the uptick.
Vaccines have already saved thousands of lives since the third wave began, drastically slashing the proportion of infected patients who are left seriously ill. But jabs aren't perfect, and admissions have been tracking upwards for a fortnight.
Almost 560 infected patients are being admitted to NHS wards each day now, compared to fewer than 100 before the Indian Delta variant took off in mid-May. The current trend in figures is above some of the gloomiest estimates from SAGE, who warned hospitalisations could breach 4,000 a day in August.
Office for National Statistics (ONS) data — based on random swab testing of thousands of people — the number of people infected with the virus in the week ending July 10 was 577,7000, up 73.5 per cent in a week
In a more positive sign, SAGE today estimated England's R rate is between 1.2 and 1.4, down from last week's figure of between 1.2 and 1.5