The estimated number of people testing positive for the virus stood at 766,500 in the week ending September 14, up 8.6 per cent from 705,800 in the previous week, according to new data from the Office for National Statistics (ONS).
Cases have also risen in Wales over the same time period, increasing from 28,200 to 39,700.
The increase brings to an end a steady fall in UK-wide infections since early July, when the total hit 3.8 million at the peak of the wave caused by the Omicron BA.4 and BA.5 subvariants of the virus.
The figures come as the number of people in hospital with Covid-19 is showing early signs of a rise.
Sarah Crofts, deputy director for the ONS Covid-19 infection survey, said: “Today's data show a mixed picture across the UK, with increases in England and Wales while infections in Scotland and Northern Ireland have decreased.
“It is too early to see if these changing trends will continue, and we will monitor the data closely to see any impact of the return of schools over the coming weeks.”
Across the UK, an estimated 927,900 people were infected with Covid-19 in the seven days to September 14, up 5 per cent from 881,200 in the previous week.
Within England, the percentage of people testing positive for Covid increased in the North East, Yorkshire and The Humber, West Midlands, and London, and continued to decrease in the South East. In all other regions of the country, the trend was uncertain in the most recent week, the ONS said.
Infection rates have also risen in children in School Year 7 to 11, as well as those aged 25 to 34 year, the ONS said. In all other age groups, the trend was described as uncertain.
Despite the rises in England and Wales, both Scotland and Northern Ireland saw a fall in cases in the week to 14 September, the ONS said.
In Scotland, 98,800 people were likely to have had Covid-19 in the latest survey, or around one in 55 - down from 113,500 or one in 45.
And in Northern Ireland the estimate is 22,900, or one in 80 people, down from 33,700, or one in 55.