BeatBullying has backed calls from the NSPCC for social media sites to do more to protect their young users.
BeatBullying founder Emma-Jane Cross said:
"This research underlines the urgent need for social networking sites to take their young users' safety much more seriously.
"We believe in the right of children to go online without fear of being bullied or harassed, and this cannot be achieved until social networks put adequate resources behind safeguarding and user verification policies."
More top news
It comes following seven days of demonstrations that have seen more than 750 people arrested.
After highs of 25C (77F) on Good Friday and 26C (79F) on Saturday, Sunday looks set to make the Easter weekend one of the warmest on record.
The top temperature could reach 26 Celsius, which would set a new record for Easter Sunday.