A survey carried out on behalf of children’s charity the NSPCC found that around 4% of young people aged 11 to 17 questioned had sent, received or been asked to send sexual content to an adult when using various sites and apps.

The charity said that one in 25 children had done so using Snapchat, Facebook or Facebook Messenger; one in 33 using Twitch and Twitter and one in 50 using Instagram and WhatsApp.

However a safeguarding expert believes these figures are only the tip of the iceberg. “It’s probably a lot worse than the figures suggest,” PC Andy Moore, who works within the safeguarding team for Thames Valley Police Slough, told HuffPost UK.

He likened the potential scale of the problem to the child sexual exploitation cases in Rotherham, Telford, Rochdale and Oxford “where it was very much underestimated”.

A total of 2,004 young people aged 11 to 17 were asked if they had ever sent messages with sexual content, been sent a naked picture or video or been asked to send these images, and the age of the person with whom they were interacting.

NSPCC chief executive Peter Wanless said: “The scale of risk that children face on social networks revealed in this research cannot be ignored and tackling it with robust and comprehensive legislation needs to be a priority for this government.

“Tech firms need to be forced to get a grip of the abuse taking place on their sites by using technology to identify suspicious behaviour and designing young people’s accounts with built-in protections.”

The NSPCC said that there are around 5.1 million young people aged 11 to 17 in the UK, and estimated that therefore around 201,000 had sent, received or been asked to send explicit messages or images.

The charity has warned that paedophiles contact large numbers of children on social media and then encourage the ones who respond to move over to encrypted messaging or live streaming.

Those who are tricked into sending images, often after being threatened, can then be blackmailed into sending more.

PC Moore, who works with local schools through their PHSE programmes, said: “A lot of children sending images are generally young girls and boys in the range of 14 and 15 [years old], and the people they’re sending them to are 17 or 18, and 18 then becomes an adult.”

He suggests the NSPCC data is likely a “conservative figure”, as children will rarely disclose what’s happening. “When you go into a school and speak to young boys and girls, you don’t always get the honest answer back,” he said, citing embarrassment as a huge barrier for preventing teens from speaking out. 

“It’s certainly a huge problem in schools, there’s no doubt about that – and I don’t think we’re close to sorting it out.”

PC Moore suggested safeguarding should be taught in schools “in the same way English and Maths are taught” – regularly rather than occasionally. “The sexual health of our children and the safeguarding of our children should be paramount in schools,” he said. “Parents are too embarrassed to do these chats so it needs to be dealt with in schools at an early age.”

Jim Gamble, CEO of Ineqe Safeguarding Group, whose Safer Schools app offers advice to teachers, parents, carers and pupils, said online grooming “is a problem that every school in the country will be familiar with”.

“It is critically important that everyone in schools – from pupils, to their parents and carers – are educated and empowered about the risks.”