Social networking sites are not doing enough to protect children from online dangers such as sexual abuse and cyber bullying, the NSPCC has warned.
The charity has accused companies of being more concerned about their profits than trying to protect youngsters from predators and bullies.
Thousands of children have asked for help in dealing with abuse on the internet and many more are at risk, it claims.
NSPCC chief executive Peter Wanless said: "We need to stand up and stop young people's lives being ruined rather than sit by and bemoan the pace of change.
"The internet is worth billions a year to the UK economy and has grown rapidly over the last 10 years, but the industry as a whole is not yet prioritising child safety in the way that it should. This just isn't good enough.
"We cannot continue to allow our young people to be groomed online by strangers or influenced by sites encouraging them to self-harm and commit suicide.
"For children, online and offline is just one world and as parents and carers we need the confidence and skills to teach them that talking to a stranger in the street is no different to talking to a stranger online."
NSPCC has teamed up with telecoms giant O2 to try to tackle the problem of online child abuse and is calling on other organisations to get involved.
The campaign will offer workshops, resources and technical advice to parents and schools to help keep children safe online.
It will also be free for O2 users to call Childline from their mobile phones.
"The internet is an amazing resource which changed all of our lives - we now communicate with each other faster and more efficiently than ever before," Mr Wanless said.
"However it has also sadly opened up a world full of dangers and risks for our children and new opportunities for those intent on exploiting them.
"We must all be alert to this threat before those that are vulnerable suffer in ways they need not."
He added: "Unfortunately the progress made by the UK telecoms industry and social media companies to help to alleviate these dangers and protect young people has been nothing like as pacy.
"As a result, thousands of children are now seeking help about online issues such as sexual abuse and cyber bullying.
"This tells us one thing - that still too many providers are more interested in expanding their services than in taking seriously their responsibilities to keep children safe online."