All London boroughs have been added to the Government's list of areas of concern as coronavirus rates continue to climb across the UK.
The new status means the capital could receive extra testing and other help such as engagement with high-risk groups as a result of rising Covid-19 cases.
Figures released in the Government's weekly surveillance report show the incidence rates in the capital, with the rate in the City of London estimated at 11.5 per 100,000 people, while in Havering it stands at 30.3.
Public Health England's (PHE) regional director for London has said the news will enable officials "to respond more rapidly and with additional measures should cases rise further and faster".
Professor Kevin Fenton said: "The placement of London on the watchlist as an area of concern is a reflection of the rising number of cases of Covid-19 being shown by a range of indicators.
"We are currently seeing much more widespread transmission in the city and being recognised as an area of concern is an important step in our efforts to control the virus."
It comes on the same day that more areas in Yorkshire and the North West learned they will be under local lockdown from Saturday.
Measures will be put in place in Wigan, Stockport, Blackpool and Leeds from midnight, meaning that people will no longer be allowed to mix with people outside their household or bubble in private homes, including gardens.
They are also advised not to meet people outside their household or bubble in any setting – whether a bar, shop or leisure facility – indoors or outdoors.
Friday was the second consecutive day of the highest number of Covid-19 cases recorded in the UK, with a further 6,874 lab-confirmed cases, taking the overall number of cases confirmed to 423,236.
The head of immunisation at PHE said rates are "stubbornly high" among young people and urged them to maintain social distancing.
Mary Ramsay said: "As students return to university, they must remember to avoid gathering in large groups and stick to the rule of six.
"The more we allow this virus to spread, the more we will see people admitted to hospital and some may die.
"We are also beginning to see more of other respiratory infections that are common in the winter – measures to control Covid will also help to reduce the risk of catching these infections."