I think the delay in starting a family is also a big factor. Anecdotal evidence (including personal experience) suggests that older parents are more anxious about their kids since, from a purely biological perspective, replacing a lost one is no longer possible. That makes people paranoid about the dangers to the kids they have. The paedo-paranoia and (my pet peeve) endless stories of dead children in the media only go fuel parental anxiety further.

So if Cameron want to stop the "corrosion of childhood", a crackdown on media outlets eliciting emotional responses to boost readership would be a better place to start.