More than 689,313 people using the NHS Covid-19 app in England and Wales were sent self-isolation alerts in the week up to 21 July.
The figures represent an increase of over 70,000 compared with the previous week's 618,903 alerts.
But the rate of increase was lower than the previous week, rising by 11% compared to 17%.
Self-isolation for all fully-vaccinated people pinged by the app as close contacts is due to end by 16 August.
In a recent interview, Business Secretary Kwasi Kwarteng told the BBC: "If you are pinged, you should self-isolate. I know it poses challenges but the rules are clear and I think they should be followed."
But the impact of self-isolation on businesses has lead for calls for the 16 August deadline to be brought forward.
The Society of Motor Manufacturers and Traders is asking for urgent assistance to exempt staff pinged by the NHS Covid app saying pings are affecting production.
The government recently expanded a scheme replace self-isolation for groups of key workers with testing.
The app alert is advisory only and not enforceable by law, unlike a phone call from the Test and Trace team.
How does the NHS Covid app work?
People in England and Wales can download the NHS Covid app (Northern Ireland and Scotland have their own).
If you are using the app and spend enough time close to another person with it, you will receive a "ping" alert if they later test positive for Covid-19 and share the information with the app. The app uses the Bluetooth signal to determine whether your phone had recently been within 2m of theirs for at least 15 minutes.
If you are "pinged" you're advised - but not legally obliged - to self-isolate for up to 10 days.
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The latest Covid App figures follow a week of falling case numbers which ended Wednesday, when 27,734 new daily cases were reported.
The Health Secretary Sajid Javid said "the truth is, when it comes to case numbers no one really knows where they are going to go next".
There have also been changes to the separate NHS App, which among other things is used for Covid vaccination records.
It has been updated to allow iPhone and iPad users to store their Covid Pass using the Apple Wallet app.
This can be used at events and venues in England, but not for international travel the government says.
BBC