The Health Secretary hit out at the lack of action taken by companies including Apple, Facebook and Google to protect youngsters' mental health, dubbing it morally wrong and deeply unfair on parents.

He accused them of failing to police underage users and has written to them demanding a response by the end of the month.

Mr Hunt said the Government would set its own limits on healthy screen time as part of a review on the impact of social media on children's mental health.

Voicing his "disappointment" at the lack of headway since discussions were held in November, Mr Hunt said: "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."