The internet can be a "playground for paedophiles", the NSPCC has warned after new figures suggested increasing numbers of children are raising concerns about online abuse and grooming.
Statistics from Childline, a service provided by the charity, show counselling sessions for youngsters worried about online sexual abuse jumped by 24% to 3,716 in 2015/16.
Most of those contacting the facility were aged between 12 and 15, and more than half were girls.
The online abuse category covers issues including grooming, sexual harassment and communications, pressure to engage in or view explicit material online and sexual extortion.
One in eight of the counselling sessions in 2015/16 were related specifically to grooming - an increase of 21%, the NSPCC said.
The charity's chief executive Peter Wanless said: "Most of us talk to people online and it's a great way to stay connected and make new friends.
"But it can be a playground for paedophiles, exposing young people to groomers who trawl social networks and online game forums exploiting any vulnerabilities they may find."
Childline founder Esther Rantzen said the internet has brought many positive changes. "But it has also brought dangers and online grooming is a real risk," she said.
Childine is launching a new campaign titled Listen To Your Selfie which is aimed at helping young people recognise the signs of grooming and unhealthy relationships, both online and offline.
Mr Wanless said: "We hope that by putting this in the spotlight we can help young people to feel able to speak up if they feel worried or scared about a situation or relationship."
A Home Office spokeswoman said: "Online child sexual exploitation is a global problem but the UK is at the forefront of efforts to combat this dreadful crime.
"The National Crime Agency (NCA) works closely with social media companies and law enforcement in the UK and overseas to identify offenders attempting to groom children online, as well as their victims.
"The NCA are also working with GCHQ to target the most technologically advanced offenders.
"We have funded further specialist teams at the NCA to tackle online child sexual exploitation which has enabled a near doubling of their investigative capability and has led to more children being safeguarded.
"The sexual exploitation of children is a heinous crime and this Government will do whatever it takes to tackle offenders and prevent abuse wherever it takes place."