Online dangers: Leeds safeguarding officials and NSPCC respond to serious incident involving pupils

The plea comes as specialist detectives continue work to identify the man who joined a group chat involving primary school pupils and committed a sexual offence.

Yesterday at least one of the city's schools issued a letter to parents to warn them about the incident and urge them to delete the live.ly app from their children's phones.

Helen Westerman, the NSPCC campaigns manager for the North of England, said: “Any app that allows strangers to approach young people is troubling – particularly where live video streaming is shared.

“It’s important to ensure children are aware of the risks of sharing explicit images and that they know how to stay safe online."

Update: Detectives hunting man who used app to perform sex act in front of Leeds schoolchildrenLeeds school alert: Pervert's sickening post as pupils chat onlineWhat Is Live.ly app?

The advice to parents was echoed by Leeds Safeguarding Children Board, which said the school had acted to make parents aware of the risk posed by the app as soon as it became aware of Monday's incident.

Independent chairman Mark Peel said: "This incident didn't take place whilst the children were in school or through using a phone app approved by the school. However, when the school was informed about the incident as a precautionary measure and from a responsible safeguarding perspective, they advised pupils not to use this app and informed parents. They also reported the matter to the police who are investigating.

"We are aware that there have been reports of similar incidents with this particular app in other areas of the country. We would, therefore, ask parents to make the necessary checks to see if this app is being used by their children, and reiterate key messages in relation to using such apps and how to keep themselves safe whilst online."

He said the board worked closely with other organisation, including Leeds City Council and the police, to educate children and inform parents about practical steps for staying safe online.

Both the NSPCC and the safeguarding board offer advice to parents about how to approach the issue.

Ms Westerman said: “We’re urging parents to talk to their children about the risks of social media. They can do this by using our Share Aware advice to help their young ones use the internet wisely and safely.

“Parents can also call the NSPCC Online Safety Helpline for any questions or concerns about social networks on 0808 800 5002.”

Advice is also available here on the safeguarding board website.