The police unit that protects children while they are on the internet says there has been a large increase in the number of reports it has received.
The Child Exploitation and Online Protection Centre - known as CEOP - believes the rise is due to greater awareness of the problem.
There were 6,291 reports last year - an increase of 880 on the previous year.
More than 1,500 were related to the online grooming of children.
Zoe Hilton, the head of safeguarding and child protection at CEOP, said the rise was down to the fact that more sites now worked with them and the introduction of a panic button meant it was easier to report incidents of concern.
CEOP encourages people to report anything they find worrying on the internet.
Ms Hilton said many children were putting themselves at risk by taking inappropriate images of themselves.
"They take an image for their boyfriend or girlfriend as a bit of fun and they don't think about where that image might end up," she said.
"What we see at CEOP is that sometimes that image ends up all over the internet, can end up on paedophile networks and forums and so it's really important to educate children about the risks of that."
The CEOP button on social networking sites links to advice on staying safe online and a place where you can report anything that may be worrying you.
The application is called ClickCEOP and is designed to help protect under 18s in the UK who use the site.
Ceop's chief executive Jim Gamble said: "What we're seeing is very early teens - sometimes even younger - and if you think about it, when you were at school when you didn't have the internet you always aspired to do the things that your older peer group did.
"And the internet allows people to do things that they perceive an anonymity that actually doesn't exist. Because this is what this is all about: stopping children from creating or adding to the risk that they may face."