More than half a million people have been ordered to isolate in England and Wales after being 'pinged' by the Covid-19 app.
Latest data shows 530,126 alerts - 520,194 in England and 9,932 in Wales - were sent in the seven days to July 7.
This is a 46 per cent rise compared to the previous week, and is the highest seven day total since data was first published in January.
The figures come amid warnings that factories are on the verge of shutting because of staff shortages caused by people having to self-isolate.
The Unite union said hundreds of employees are off work at some sites, especially in the automotive sector, with alerts from the NHS app causing "havoc" on production lines.
Yesterday The Mirror reported that singer Ed Sheeran was among those ordered to stay at home for 10 days after coming into contact with a positive case.
Despite the rise in the number of people getting "pinged" there were more downloads of the app in the seven days to July 7 (342,483) than in any week since the seven days to June 6 (393,842).
Separate figures published today showed nearly one in seven people transferred to the Test and Trace system in England after testing positive for Covid-19 are not being reached.
This is the highest proportion not reached since the middle of October last year.
Some 13.7% of people transferred to Test and Trace in the week to July 7 were not reached, according to the Department of Health and Social Care.
The figure has not been this high since the week ending October 21, when it stood at 14.5%.
Anybody in England who tests positive for Covid-19, either through a rapid (LFD) test or a PCR test processed in a laboratory, is transferred to Test and Trace so their contacts can be traced and alerted.
Some 86.1% of these people were reached in the latest week.
A total of 194,005 people tested positive for Covid-19 in England at least once in the week to July 7.
This is up 43% on the previous week, and is the highest number of people testing positive since the week to January 27.
The latest data suggests the Test and Trace system is facing pressures similar to those seen during the second wave of the virus last winter.
Just under two-thirds (63.0%) of people who were tested for Covid-19 in England in the week ending July 7 at a regional site, local site or mobile testing unit - a so-called "in-person" test - received their result within 24 hours.
This is down from 76.9% the previous week and is the lowest percentage since the week to January 13.
Prime Minister Boris Johnson had pledged that, by the end of June 2020, the results of all in-person tests would be back within 24 hours.
He told the House of Commons on June 3 2020 he would get "all tests turned around within 24 hours by the end of June, except for difficulties with postal tests or insuperable problems like that".
A Department of Health and Social Care spokesperson said: “The NHS COVID-19 app has been downloaded more than 26 million times, saved thousands of lives and stopped hundreds of thousands of cases by doing exactly what it is designed to do - informing close contacts of someone who has tested positive for COVID-19 they are at risk and advising them to isolate.
"In the context of rising cases it is vital people are aware of their personal risk so they can make informed decisions on their behaviour to protect those around them.”
