The reproduction rate of coronavirus (R number) could have tipped above 1.0 in the capital, meaning the spread of the virus could now be increasing rather than decreasing.
The R number for the UK as a whole has risen to between 0.8 and 1.0, up from the previous week's number of 0.8 - 0.9.
In London, its estimated that the R number is between 0.8 and 1.1.
It is also thought that the R number could have tipped above 1.0 in the South West and the North West.
An R number below 1.0 is crucial for scientists to have confidence that the prevalence of coronavirus is going down in Britain.
If the number is above 1.0 it means each person with the virus will pass it on to more than 1.0 person.
For example, if the number is 1.1, it means each person with coronavirus is passing it to 1.1 people.
When the UK was under full national lockdown, ministers said the R number needed to be consistently below 1.0 before restrictions could be lifted.
A local lockdown has already been placed on large parts of the North West and the estimated R number in London will be a cause of concern for local officials hoping to avoid new restrictions.
The latest growth rate range for the UK is 0% to -5%.
A growth rate between 0% to -5% means the number of new infections is somewhere between remaining stable and shrinking by 5% every day.
But there is much fluctuation in the estimated growth rates for England's regions.
The growth rate reflects how quickly the number of infections are changing day by day.
It is an approximation of the percentage change in the number infections each day.
If the growth rate is greater than zero (+positive), then the epidemic is growing. If the growth rate is less than zero (- negative) then the epidemic is shrinking.
Regional growth rates outside of the capital:
East of England -4 to -1
Midlands -3 to 0
North East and Yorkshore -4 to 0
North West -3 to +1
South East -4 to 0
South West -3 to +3
The NHS warned that R numbers and growth rates should be taken with a pinch of salt in certain situations.
It said estimates of R "become insufficiently robust to inform policy decisions" when the "number of cases falls to low levels and/or there is a high degree of variability in transmission across a region".
The NHS said this is the case in the East of England, London, the Midlands, the North East and Yorkshire, and the South West.
It comes as new figures from the ONS show the percentage of individuals testing positive for Covid-19 has risen since lockdown was lifted at the end of June, but it said there is now evidence to suggest that this trend may have levelled off.