Schools should be phone-free throughout the entire day, the education secretary has told headteachers in England, stressing that pupils should not use the devices even as calculators or for research.

Bridget Phillipson wrote to schools to underline updated guidance issued by the government last week, according to the BBC.

“Schools should make sure those policies are applied consistently across classes, and at all times and we want parents to back these policies too,” Phillipson said.

Teachers were also advised not to use their phones in front of pupils.

Phillipson said Ofsted, the schools watchdog, would inspect how schools implement the policy, while the Department for Science, Innovation and Technology (DSIT) said it would take immediate action on children’s social media use.

The updated guidance states that pupils “should not have access to their devices during lessons, break times, lunchtimes or between lessons”.

DSIT data shows 99.9% of primary schools and 90% of secondary schools already have mobile phone policies. However, 58% of secondary school pupils reported phones being used without permission in some lessons, rising to 65% among key stage four pupils.

Paul Whiteman, the general secretary of the National Association of Head Teachers, told the BBC school leaders “need support from government, not the threat of heavy-handed inspection”.

The move comes as ministers consult on introducing an Australian-style social media ban for under-16s in the UK. Options include raising the digital age of consent and restricting potentially addictive app design features such as “streaks” and “infinite scrolling”.

Ministers will visit Australia, where a ban came into force in December. The government will seek views from parents and young people and will respond in the summer, according to the DSIT.

Last week, the House of Lords backed a Conservative-led amendment to the children’s wellbeing and schools bill that proposed such a ban, despite it not being supported by the government.

While ministers’ plans to bring forward legislation mean the amendment is unlikely to survive in the Commons, its passage in the upper chamber has increased pressure on the prime minister to act more quickly and decisively. Keir Starmer is understood to want to wait for evidence from Australia’s ban.