Coronavirus cases in the community rocketed by 76.5% in just one week, according to official estimates for England.
Around one in 640 people in private households had COVID-19 in the week to 29 May – up from one in 1,120 in the previous week, said the Office for National Statistics.
This is the highest level since the week to 16 April and represents a 76.5% increase.
Live COVID updates from the UK and around the world
The figures are likely to be among the data considered by the prime minister as he decides on whether to drop coronavirus restrictions on 21 June.
Boris Johnson is under pressure to press ahead with the unlocking – dubbed “freedom day” by some – following the successful rollout of vaccines.
However, concerns persist over the spread of the Indian variant, also known as the Delta variant.
In Wales, there also are “early signs” of an increase in the percentage of people testing positive for coronavirus, with around one in 1,050 people estimated to have had COVID-19 in the week to 29 May, the ONS said.
This is up from one in 3,850 in the previous week and is the highest estimate since the week to 16 April.
In Northern Ireland the trend is “uncertain”, with an estimate of around one in 800 for the week to 29 May, broadly unchanged from one in 820 in the previous week.
The trend is also “uncertain” for Scotland, where the latest estimate is around one in 680, broadly unchanged from one in 630.
All figures are for people in private households.
The percentage of people testing positive for COVID-19 is estimated to have increased in North West England, the East Midlands and South West England.
There are also signs of a possible increase in the West Midlands and London while the trend is uncertain for other regions, the ONS said.
In many regions positivity rates are very low, meaning trends are difficult to identify since they are affected by small changes in the number of people testing positive from week to week.
The North West had the highest proportion of people of any region in England likely to test positive for coronavirus in the week to 29 May – around one in 280.
South East England had the lowest estimate – around one in 1,490.