The internet can be "a playground for paedophiles", the NSPCC has warned. The warning came as figures showed a rise in children, worried about online abuse and grooming, contacting the charity's Childline service.
Counselling sessions for young people worried about online sexual abuse rose 24% to 3,716 in 2015-16. The Home Office described it as "a global problem" adding that "the UK is at the forefront of efforts to combat this dreadful crime".
"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."
Mr Wanless he said that he hoped that by putting the issue into the spotlight, more people would feel able to speak up if they were worried or scared by a situation or relationship.
Childline founder Esther Rantzen said the internet had brought many positive changes but added: "It has also brought dangers and online grooming is a real risk." The charity's new Listen To Your Selfie campaign aims to help young people recognise the signs of grooming and unhealthy relationships.
It includes two films where selfies come to life and question a situation. The Game focuses on a same-sex online grooming scenario and The Party highlights peer-to-peer sexual pressure and grooming.
One 16-year-old girl said her boyfriend was older and made her share images with his friends online. "He gives me money and food when I go online and do things via webcam. I have not told anyone else what is happening, I am so scared and drink to forget. I just know I am not normal, I am weird and nobody understands. I am disgusting, so rather me than another young girl."
A 15-year-old boy feared he was being groomed by a man he had met online. "He has asked for pictures and one time I made the mistake of sending a nude selfie. He won't show me any pictures of him, which makes me think he is fake. I have not agreed to meet him because I am scared. He has threatened to show my nude selfie to the world. I am gay, but nobody knows, so it would ruin me if people found out. I cry myself to sleep every night with worry."
A Home Office spokeswoman said the National Crime Agency was working closely with social media companies and police in the UK and overseas to identify offenders and their victims, with GCHQ helping target the most technologically advanced offenders and specialist funding almost doubled. "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," said the spokeswoman.