More than half a million people in England were pinged by the NHS Test and Trace app in a week, the highest figure recorded.
A total of 520,194 alerts were sent to users of the NHS COVID-19 app in the week to July 7, telling them they had been in close contact with someone who had tested positive for coronavirus and to self-isolate.
This is up from 356,677 the previous week – a rise of 46% – and is the highest weekly figure since data was first published in January.
It comes as some companies are reportedly missing 20% of their workers.
Factories across Britain are in danger of closing down as a result of employees being "pinged" by the app, union Unite warned.
The union said large numbers of workers are being told to self-isolate, with companies in the automotive industry particularly affected.
This morning Communities Secretary Robert Jenrick said the government is "concerned" about the number of people off work due to being "pinged" by the app.
Mr Jenrick told LBC radio today: "It is important that we have the app, that we take it seriously, that when we do get those messages we act accordingly."
But he said ministers would give "further thought" on how the government can ensure it is a "proportionate response".
He added: "We are concerned about absences as a result of being pinged, for example. That is one of the reasons why we do need to move to a more proportionate approach."
Mr Jenrick was forced to defend the government’s handling of COVID-19 rules, branded a "total shambles".
He insisted the nation is moving into a "new phase" where "we all exercise our personal judgement".
But Welsh First Minister Mark Drakeford said it is "difficult" for people in England to know exactly what is required of them.
And he urged Westminster to follow a four-nation approach.
"It is the UK government that is the outlier and if they were prepared to bring themselves into line with the decisions that have been made in Scotland and in Wales, for example, that would be clearer and simpler for everybody," Mr Drakeford told Good Morning Britain.
The TUC slammed the official guidance as a "recipe for chaos and rising infections".
And shop workers union Usdaw described it as a "real mess", offering no assurances for employees or customers.
Meanwhile Dr Roger Barker, policy director at the Institute of Directors, said firms are "understandably confused" by the government’s "mixed messages and patchwork requirements".