Cyber bullying has more than doubled in a year and more than one in three children are now victims.
A survey of 11 to 17-year-olds found 35 per cent reported that they have experienced cyber bullying - compared with 16 per cent last year.
Four in 10 said they'd seen others being picked on online - almost double the 22 per cent recorded last year.
Internet security firm McAfee polled 2,000 UK children and 2,000 adults. It also found apps like SnapChat and dating app Tinder are now used by children - many aged 15 or under - on a daily basis.
Some 17 per cent of the teenagers polled admitted to using Tinder - a dating app which allows users to select a potential partner based on photos - every day, but almost half of those (46 of males.
Tinder subscribers are shown other users close to their location. If they like the look of them, they give them a tick and if they receive one back, they can start communicating with each other.
It is open to anyone aged 13 or older, with under-18s only able to match with people in the same age bracket.
The data was published ahead of Anti-Bullying Week, which starts on Monday, and compared the findings with a similar study carried out last year.
Parents are becoming more relaxed in their attitude towards the internet and social media, with many helping their children to set up accounts on sites with an age limit, the poll revealed.
According to the study:
• Less than a third of parents (27 per cent) said they were worried about their child being the victim of cyber-bullying this year. That number had almost halved from 45 per cent in the previous year.
• Another two-thirds (67 per cent) of children are now allowed to go online without supervision - up from 53 per cent.
• However, more than three-quarters (77 per cent) of mums and dad polled said they had conversations about online safety, up from 68 per cent last year.
Andy Phippen, professor of social responsibility in IT at Plymouth University, said there was 'a real gap' emerging between parental concern and what children faced online every day.
He said: "While it is encouraging to see that these conversations are happening, there are areas in which parents may not be completely aware of their children's online behaviour.
"It's now time for parents to take the conversations to the next level and become further educated on the social platforms that exist, what ages they are suited for and what type of behaviour they encourage.
"Cyber-bullying happens across all platforms and children's use of social media is transient."
Claire Lilley, head of child safety online at the NSPCC, said cyber-bullying is a 'huge concern'.
She added: "The use of teen dating apps can expose children to contact by adults who have a sexual interest in them because the age controls are often inadequate.
A spokeswoman for Tinder said there were restrictions on how under-18s could use the dating app: "You must have an official Facebook account in order to join Tinder.
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