To use adult dating
Many adult dating sites focus on the local aspect of finding a match.Some users regard the service as no different from finding a one-night stand on a night out.
Claire Lilley, head of child safety online at the NSPCC, said cyber-bullying is a "huge concern".
It is open to those who are 13 or older, with under-18s only able to match with people in the same age bracket.
Andy Phippen, professor of social responsibility in IT at Plymouth University, said: "It is very concerning to see the proportion of younger teens using apps like Tinder, whose aim is essentially hook-ups and dating, and very much for an adult audience.
"These apps also share location-based information and can be used as platforms for grooming and abuse." The researchers found an increasingly relaxed attitude from parents toward the risks posed online despite the fact that the number of children being bullied on the internet has doubled this year - 35% reported that they have experienced cyber-bullying compared with 16% last year.
Four in 10 said they had witnessed others being picked on online - almost double the 22% recorded last year.