Digital giants Facebook, Twitter and Google have united to reject an Abbott government proposal that would force social media companies to remove content deemed harmful to young people.

The government has proposed appointing a children's e-safety commissioner with the power to force sites to take down posts containing bullying or harassment -an idea backed by child psychologists and family groups. The government is also considering creating a new Commonwealth cyber-bullying offence.

The Australian Interactive Media Industry Association - representing the major social media companies - says the proposal is too cumbersome and would not cover popular messaging services such as Snapchat and Kik.

NSW Police recently described Kik, a texting app that allows people to connect with strangers, as "the number one social media problem involving teenagers''.

''A policy that clamps down heavily on the things that young people can say to each other on larger responsible sites has potential to drive young people to engage in risk-taking behaviour on services that have less well-developed protections in place and are not covered by the legislated scheme,'' the association said in its submission to the government.