NHS chiefs are looking to cut the sensitivity of their Covid-19 app in England, as politicians fear workplace chaos if millions of people are told to self-isolate after being exposed to the disease.

Sajid Javid, health secretary, has backed the review as Conservative MPs warned that the economy and public services could face heavy disruption if, as expected, most final Covid restrictions are lifted on July 19.

Ministers have been warned that millions of people could be “pinged” by the app to tell them they had been in close contact with a positive Covid case; Javid has conceded cases could rise to a record 100,000 a day this summer.

Amid signs that people are starting to delete the NHS Covid app to avoid being told to self-isolate, Jenny Harries, head of the UK health security agency, said a review was under way into how it operates.

She told the House of Commons public accounts committee that the app could be “tuned” to ensure it was there “for a purpose, not for annoyance” and to reflect the fact the population was increasingly vaccinated.

“We have a piece of work ongoing at the moment because it is entirely possible to tune the app to ensure it is appropriate to the risk,” she told MPs.

Health officials said the review would reduce the sensitivity of the app, which uses Bluetooth technology to assess proximity and length of time a person is exposed to someone who tests positive for Covid.

Rishi Sunak, chancellor, said that the public were “frustrated” at the regularity with which they were being asked to go into 10 days of self-isolation, disrupting work and travel plans.

UK Hospitality, the industry body, said that at any one time up to one-third of all staff were self-isolating. Hospitals fear staff shortages just as Covid cases are starting to rise sharply.

The Financial Times reported this week that recent data suggest that two people are asked to self-isolate for every confirmed Covid case. With ministers expecting up to 700,000 cases a week, that would imply a further 1.4m people a week would be asked to stay at home for 10 days.

Tory MPs are increasingly worried about the implications for the economy and for families planning holidays.

Javid announced this week that the self-isolation regime would be replaced on August 16 with a new regime for double-jabbed individuals, based on testing.

But the health secretary agreed that the new system should not be introduced immediately on July 19, fearing that case numbers would increase even more quickly than currently expected.

The UK has recorded 33,551 new coronavirus cases, according to the government’s Covid dashboard on Thursday. Ministers have admitted that daily total could reach 50,000 by July 19 and then rise to 100,000. There were 35 new deaths, up 52 per cent week on week.

Meanwhile, The Guardian reported that hospitals were again having to cancel operations, including cancer surgery, because they were treating a growing number of patients with Covid or because medical staff were self-isolating.