New laws to crack down on social media giants that allow flagrant breaches of age limits are being considered by ministers.
In a strongly-worded letter to platforms like Facebook and Google, Health Secretary Jeremy Hunt has accused companies of "turning a blind eye" to a generation of children who are being "exposed to harmful emotional side effects" of social media use.
The firms have been given just over a week to set out what steps they have taken to cut underage use, prevent cyber bullying and encourage healthy screen time, and what more they intend to do.
The Health Secretary warned that the failure of platforms to prevent young children using social media was "unacceptable and irresponsible".
He wrote: "In particular, progress on age verification is not good enough. I am concerned that your companies seem content with a situation where thousands of users breach your own terms and conditions on the minimum user age.
"I fear that you are collectively turning a blind eye to a whole generation of children being exposed to the harmful emotional side effects of social media prematurely.
"This is both morally wrong and deeply unfair to parents who are faced with the invidious choice of allowing children to use platforms they are too young to access, or excluding them from social interaction that often the majority of their peers are engaging in.
"It is unacceptable and irresponsible for you to put parents in this position."
The Health Secretary questioned whether social media giants had "sufficient will" to introduce solutions.
Mr Hunt stressed that the Government does not rule out bringing in new legislation to deal with the situation when it considers options in May.
The intervention comes six months after the Health Secretary set in train a working group on children and young people's mental health and social media that involved Facebook, Snapchat, Google and others.
In December, the Health Secretary publicly attacked Facebook for releasing a version aimed at children, telling the company to "stay away from my kids".
An evidence-based review by the Chief Medical Officer on the impact of technology on the mental health of children and young people has also been launched by Mr Hunt.