Quarter of children 'see online sex content'
Some 25 per cent of 13 to 15-year-olds have seen sexually explicit images online, while 28 per cent have been sent sexual pictures on a mobile phone.
More than one in four 10 to 12-year-olds said they had read alcohol-related posts on social networking sites, while 37 per cent of 13 to 15-year-olds have viewed photos of their friends drunk.
And 13 per cent of 13 to 15-year-olds admitted they had come under pressure to drink alcohol.
The poll, of 800 parents and 600 children, was carried out for the industry-funded charity Drinkaware and parenting charity Family Lives, both of which expressed concern at the results.
Jeremy Todd, chief executive of Family Lives, said: "While families have always worried about their children's use of existing and emerging technologies, social networking is a relatively new phenomenon that did not exist for most parents when they were at school.
"Family Lives encourages parents to have conversations with their children, as the consequences of inappropriate social networking and messaging amongst children and young people can be extremely damaging.
"Young people are more likely to seek help and advice from parents who listen and are supportive, rather than those who lecture or fly off the handle."
Chris Sorek, chief executive of Drinkaware, said: "With children as young as 10 being exposed to conversations about alcohol both on and offline, it's essential parents feel equipped to talk to them about the risks of underage drinking."