The weekly number of positive COVID-19 cases in England in late August was the highest since the end of May, the latest data from the test and trace scheme showed on Thursday.
NHS Test and Trace said 6,732 new people tested positive for COVID-19 in England between 20 August and 26 August - an increase of 6% in positive cases compared to the previous week.
Last week’s figures had shown the first decline in weekly COVID-19 cases since July.
There was an increase in the number of positive cases reached under the system, up to 81.4% from 75.2%, in the latest weekly figures, but a fall in the proportion of their contacts that were reached, down to 69.4% from 77.1%.
The test and trace scheme is seen as key to locating outbreaks quickly as British Prime Minister Boris Johnson looks to restore life in most of the country to normality while using local lockdowns to reduce transmission in COVID-19 hotspots.
Britain has also increased its capacity for testing since May.