The children's support service Childline has reported a surge in the number of children contacting them about online bullying.
More than 1,400 young people said they were experiencing racist bullying, up 69% on the previous year.
The charity's founder Esther Rantzen said these findings are a wake up call.
A common theme was for young people to be called a "terrorist" or a "bomber" and to be told to "go back to where they came from," Ms Rantzen said.
The 24-hour phone and online support service also reported number of contacts from suicidal young people increased by a third in a year.
Deputy Commissioner Craig Mackey told members of the Greater London Assembly that the force has seen a rise in crimes linked to online harassment and bullying.
This follows a number of high profile cases of "Twitter trolling", where users of the site are bombarded with threats and abuse.
Mr Mackey said: "We're seeing about 1,500 additional offences reported to us per year. I think it will rise as people become more aware of this."
Online shopping accounts for 10.8% of all retail sales which is the highest since record began in 2006, according to the Office for National Statistics.
The Child Exploitation and Online Protection (CEOP) Centre has created a new interactive film, First to a Million which focuses on young people who post video content online.
The film highlights how quickly uploaded internet material can spiral out of control and where young people can get help if it does.
The video deals with a range of scenarios that young people might face, including sexually explicit material.
Research shows that 88% of self-generated, sexually explicit online images and videos of young people are taken from their original location and uploaded onto other websites.
CEOP's video can be viewed here: