The government says it's "extremely concerned" about the increase in cyber-bullying and the Law Commission has been asked to fast track recommendations to curb it.

Justice Minister Judith Collins says young people are increasingly enmeshed in social media and cyber-bullying can have devastating effects.

"I'm concerned we treat this as a priority and take action to reduce the potential for harm where we can," she said on Friday.

The Law Commission is looking at:

• Introducing a new offence of maliciously impersonating another person on the web

• Making sure the Harassment Act applies to cyber-bullying and other online intimidation

• Extending the Telecommunications Act's definition of misuse of a telephone to also cover computers and other electronic devices.