A Conservative MP has suggested that under-16s should be banned from using smartphones for the sake of their mental health.
She said there had been a "marked increase" in poor teenage mental health since 2010, and that it was "time to consider banning social media and perhaps even smartphones for under 16s?"
Ms Cates appeared to reference the case of Mia Janin, a 14-year-old who is believed to have killed herself.
Her father, Mariano Janin, believes she was bullied online by other pupils at the Jewish Free School, in Kenton, London, where she was a Year 10 student.
One child told the inquest into her death that a post from Mia on TikTok was shared to a Snapchat group run by male pupils at the school, where they made fun of her.
Speaking in the Commons, Ms Cates said: "This morning, the press reported the tragic case of a 14-year-old girl who took her own life following horrific social media bullying, including on TikTok and Snapchat.
"Since 2010, across the English-speaking world, there's been a marked increase in poor teen mental health, teen suicide attempts and children addicted to pornography.
"The United Kingdom has a strong tradition of legislating to protect children from serious threats to their safety and welfare.
"So does my right honourable friend agree with me that it's time to consider banning social media and perhaps even smartphones for under 16s?"
The prime minister said that Ms Cates was "absolutely right to highlight the impact of what happens online to our children".
"And that's why our Online Safety Act tackles both criminal activity online and protects children from harmful or inappropriate content such as bullying or the promotion of self-harm and accessing pornography and also exposure to eating disorders," he said.
"Ofcom are now rightly developing and consulting on the guidance and the codes of practices for how those platforms will meet their duties and if they don't clean up their act then Ofcom will be able to impose fines of up to 10% of global turnover on the social media firms."
Anyone feeling emotionally distressed or suicidal can call Samaritans for help on 116 123 or email email@example.com. Alternatively, letters can be mailed to: Freepost SAMARITANS LETTERS.