Cases of the Indian coronavirus variant have increased 79 per cent in a week, Public Health England (PHE) said.
The mutation that originated in India is now believed to be dominant in the UK, with 12,431 cases now confirmed.
PHE said early evidence suggests there may be an increased risk of hospital admission from the variant.
Figures showed there were 278 people with the variant who attended hospital emergency departments this week, up from 201 last week.
There were 94 overnight hospital admissions for patients with the Indian variant, up from 43 admissions the previous week.
The majority of those admitted to hospital had not received a coronavirus vaccination.
Dr Jenny Harries, chief executive of the UK Health Security Agency, said: “With this variant now dominant across the UK, it remains vital that we continue to exercise caution particularly while we learn more about transmission and health impacts.
“The way to tackle variants is to use the same measures to reduce the risk of transmission of Covid-19 we have used before. Work from home where you can, and practise hands, face, space, fresh air at all times.
“If you are eligible and have not already done so, please come forward to be vaccinated and make sure you get your second jab. It will save lives.”
PHE said the area worst affected by the Indian variant remains Bolton, where cases have risen by 795 from last week to a total of 2,149.
Blackburn with Darwen is the second worst affected area where cases of the variant have jumped by 368 week-on-week to a total of 724.
But PHE said there were “encouraging signs” the transmission rate in Bolton was beginning to fall following actions taken by the local authority and residents, including teams of health workers going door-to-door to encourage people to get vaccinated at drop-in centres.