The NASUWT teaching union has written to health secretary Matt Hancock about “deeply worrying” evidence that some teachers are being told to “pause” tracing on the Covid app.

The union says the instruction is “risking lives”. It has shared an email with Tes in which a public health official on the Wirral tells local headteachers to get staff to disable the NHS test-and-trace app while in school.

And it believes that this may be happening across the country.

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“Given that we now have a well-established local system for contact tracing of school-notified cases, we are recommending that you advise any staff/pupils that have downloaded the NHS COVID-19 app to pause the contact-tracing function of that app while they are on the school premises,” the Wirral email tells heads.

But NASUWT general secretary Patrick Roach says that government instructions for the use of the app clearly state it should switched on at all times in schools unless the phone is in a locker.

“It beggars belief that some schools are disregarding such clear instructions and it is deeply worrying that local public health teams appear to be giving similar advice,” he said.

In his letter to Mr Hancock, Dr Roach states: “We assume that this action is not limited to this one local public health team, given the range and number of concerns raised [by our members].”

A statement from the union leader adds: “Even more concerning is that some teachers are being told to disregard app notifications to self-isolate, apparently in order to reduce the numbers of staff and pupils self-isolating.

“A key aspect of controlling the virus is an effective test-and-trace system, of which the app is an integral part.

“Schools and authorities overriding advice are putting at risk the safety and the lives of teachers and pupils and risking much larger outbreaks. This would lead to far more pupils and teachers self-isolating than would be required if the app was followed.

“The government’s test and trace system is already beset with problems, and ministers must act swiftly and with clarity to ensure that schools are following the correct guidance at all times and teachers have the app switched on in schools.”

Government guidance to teachers about the test and trace app in schools states there are only three situations when tracing should be paused, which are: 

• When someone is not able to have their phone with them, for example because it is stored in a locker or communal area - this is to avoid the app picking up contacts when the user is not with their phone.
• When someone is working behind a perspex (or equivalent) screen, fully protected from other colleagues and members of the public, as they are considered to be adequately protected from contracting the coronavirus.
• In a health or care setting where staff are wearing medical-grade personal protective equipment (for example, a surgical mask) as these individuals are also considered to be adequately protected.

Dr Roach’s letter calls on the government to issue “immediate instruction to all schools and public health teams stating that there must be no instructions given to disable the app while in school unless one of the three criteria are met”.

A Wirral Council spokesperson said: “The advice given was based on a well-established national approach to minimising the potential for false notifications of close contact with a case.

“The advice - detailed on the government’s website - says contact tracing within the app should be paused when your phone is stored in a locker or other communal area.

“Wirral schools have a very effective local process for contact-tracing when cases are notified on their premises and the advice issued to headteachers clearly states that the contact tracing toggle on the app should be turned back on as soon as they leave the school setting.”

The DfE has been contacted for comment.