The plans, among the toughest online safety restrictions proposed anywhere in the world, will also target gaming and livestreaming services that allow children to communicate with strangers.
Announcing the policy at a Downing Street press conference on Monday (15.06.26), Starmer said the changes reflected Britain's values and would help protect young people from the harms associated with excessive online use.
He said: "It is clear to me a full ban is the right choice.
"This will change the conversations that parents have and the expectations of children over time. It will make a huge difference, it will make our children safer, it will make our children happier, it will give them more time, more security, more freedom to grow up, more opportunity."
The ban is expected to cover major platforms including TikTok, Snapchat and Instagram.
Starmer also pledged action against online gaming and livestreaming services that enable children to interact with unknown adults.
The Labour leader said: "Is there a situation in the offline world where you would just let your child pair up with a stranger, an adult that you don’t know anything about?
"No, so we’re taking action on that."
The Prime Minister said the government already had powers to begin implementing elements of the restrictions, with further regulation due by the end of the year and the full ban expected to take effect next spring.
Britain has progressively tightened its approach towards technology companies through measures including age verification requirements and restrictions on harmful content.
However, concerns over the impact of social media on children's mental health prompted ministers to go further after reviewing evidence from countries including Australia, which introduced its own under-16 social media ban last year.
The government said its consultation received more than 116,000 responses from parents, young people and industry representatives.
More than 83 per cent of parents who responded believed the risks of social media outweighed the benefits, while 90 per cent supported introducing a minimum age of 16.
Despite widespread support, some psychologists and researchers have questioned whether blanket bans are effective, arguing there remains limited evidence they improve outcomes for children.
