There has been a 17 per cent increase in the number of people testing positive for coronavirus in the past week as officials target testing in virus hot spots.
New data from England’s test and trace service shows the rise in positive cases comes despite the number of people overall being tested rising just four per cent.
Officials say the rise corresponds with the targeted testing for areas where there is known outbreaks in cases but that the increase also reflects the overall rise in incidence of the virus.
Last week the Office for National Statistics said the numbers of infections were rising with daily cases having risen from an estimated 3,200 to 4,200 at the end of July.
Overall, 4,642 people were transferred to the contract tracing system in the last week, with 79 per cent reached by contact tracers.
Of those spoken to, 19,150 people were identified as coming into close contact with someone who has tested positive.
Of these, 72 per cent were reached and asked to self-isolate, a drop from 76 per cent in the previous week.
The test and trace figures show the national call centres are still struggling to reach contacts. Only 56 per cent of close contacts handled online or by call centres were reached and told to self-isolate for 10 days.
In comparison, local health protection teams have been more successful, reaching 98 per cent of close contacts of people who tested positive.
In recent weeks local health officials have criticised the national centralised service for failing to reach enough close contacts, including in areas hit the worst by the virus such as parts of the north west of England.
There is now a push to recruit more people to local health protection teams and local councils have been given increased access to patient level data in order to carry out their own local test and trace service.
More than three quarters of people who were tested at a regional testing site for Covid-19 received their result within 24 hours, but overall 97 per cent of results were communicated the next day if not within 24 hours.
Since the launch of test and trace, 199,524 close contacts of people who have tested positive for Covid-19 have been reached through the tracing system and asked to self-isolate.
This is 82.2 per cent of a total of 242,749 people identified as close contacts.
Scientists on the government's SAGE committee have said the service must reach 80 per cent in order to be useful in curtailing the spread of the virus.
The remaining 43,225 people were identified as close contacts, but were not reached.
Executive chair of NHS Test and Trace Baroness Dido Harding said: "Test and Trace is working. It has already helped to prevent almost a quarter of a million people unknowingly spreading the virus. But we do not work alone. Close partnerships with local government and local public health teams are essential to stop the spread of the virus, and NHS Test and Trace continues to work hand-in-hand to support communities experiencing spikes in cases, through increased testing and additional contact tracing.
“Winter may seem far away but it’s what we do right now that counts. So please do play your part to stop the virus from flaring up again – this system will only work if you come forward for a test and help us to trace your contacts. So if you have symptoms, however mild, get a free test immediately. If you are contacted by NHS Test and Trace, follow the advice you receive. This is how, together, we’ll get back to the things we love.”