Children are using false ages online and seeing restricted adverts for overtly sexual dating sites, gambling, alcohol and slimming aids, a study has found.
A survey by the Advertising Standards Authority (ASA) found all but four of the 24 children aged between 11 and 15 who participated in the study registered on a social media site using a false age.
The study, commissioned by the advertising regulator to find out what ads young people see and engage with online, found that 10 participants (42%) falsely registered themselves as aged 18 or over, while nine were aged below the permitted age of registration on at least one social media site.
Of the 218 ads served to those registered as over 18, 24 (11%) were for products that "must not be directed at people under 18 through the selection of media or the context in which they appear".
The study found that 98% of the 427 ads seen by the participants adhered to the relevant rules, and advertisers were acting in good faith by taking account of the registered age of social media account holders, the ASA said.
However many of the children saw ads for age-restricted products, such as gambling, alcohol, slimming aids and overtly sexual dating services, because they had used a false age to register.
The ASA said it would present the findings to its council "with a view to exploring whether we need to take a tighter line on age-restricted ads in social media", and would also ask the body that writes the Advertising Code, the Committee of Advertising Practice, whether new guidance on targeting ads online is needed.
The watchdog said: "Our report clearly asks questions of social media owners around the effectiveness of age-verification and whether enough is being done to prevent children from accessing age-restricted content on social media sites.
"We will be raising these issues with social media companies."
ASA chief executive Guy Parker said: "On the face of it, our survey suggests that advertisers are sticking to the rules but children aren't.
"But before we all lay the blame with parents and guardians, we need to be honest. If advertisers and social media companies know that children say they're older than they are, don't they have a crucial part to play too?
"We'll be talking to them about self-declared age-gating and considering whether we need to take a tougher line. But we all need to be part of this conversation about how best to set the boundaries within which our children explore the world around them."