Keir Starmer is vowing to enforce a crackdown on children and teenagers using smartphones within months to help keep them safe online.
Reforms could include a minimum age limit for social media and restrictions on so-called “infinite” scrolling.
Children could also be prevented from using virtual private networks (VPNs) to illicitly access pornography, and from speaking with online chatbots under proposals in a government consultation.
Ministers are taking steps now to bring in powers that mean they can act swiftly and respond to its results within months.
Before that, they will act now to close a legal loophole and force all AI chatbot providers to abide by the Online Safety Act or face the consequences of breaking the law.
It follows a war of words between ministers and Elon Musk after his Grok AI chatbot was used widely to make fake nude images of women.
The PM pledged that no online platform would get a “free pass” when it comes to children’s safety on the internet.
Sir Keir said: “As a dad of two teenagers, I know the challenges and the worries that parents face making sure their kids are safe online. Technology is moving really fast, and the law has got to keep up. With my government, Britain will be a leader, not a follower, when it comes to online safety.
“The action we took on Grok sent a clear message that no platform gets a free pass.
“Today we are closing loopholes that put children at risk, and laying the groundwork for further action. We are acting to protect children’s wellbeing and help parents to navigate the minefield of social media.”
The consultation into new social media protections will launch in March and be guided by what parents and children say they want to see.
Ministers also plan to introduce powers through the Children’s Wellbeing and Schools Bill to speedily change the law in reactions to changing online behaviours.
Elsewhere, amendments to the Crime and Policing Bill will be used to ensure chatbots protect users from illegal content.
Technology secretary Liz Kendall said: “I know that parents across the country want us to act urgently to keep their children safe online. That’s why I stood up to Grok and Elon Musk when they flouted British laws and British values.
“We will not wait to take the action families need, so we will tighten the rules on AI chatbots and we are laying the ground so we can act at pace on the results of the consultation on young people and social media.
“We are determined to give children the childhood they deserve and to prepare them for the future at a time of rapid technological change.”
The Crime and Policing Bill will also be updated to include measures which will preserve children’s social media and online data, as called for by the campaign group Jools’ Law.
The campaign was started by Ellen Roome, when questions about the death of her 14-year-old son Jools could not be answered as records of his digital activity could not be accessed.
Lord Nash, a Conservative former minister who has been campaigning in the Lords for tighter social media controls for children, welcomed the adoption of Jools’ Law by the government.
He added: “However, we have a moral duty to try and ensure it is never needed in future by avoiding future tragedies.
“There are too many children who are still being catastrophically harmed by social media every day, and this announcement will not prevent that. This consultation is just delay dressed up as process.
“Instead of more deliberation, the government must raise the age limit to 16 for the most harmful platforms now and has the opportunity to do so when the amendment effecting this – which passed overwhelmingly in the House of Lords – returns to the Commons. For every day we delay, the more children we fail.”
The Tories accused ministers of inaction and said the announcement was “more smoke and mirrors”.
Laura Trott, the shadow education secretary, added: “Claiming they are taking ‘immediate action’ is simply not credible when their so-called urgent consultation does not even exist.“
Australia became the first country in the world to prohibit social media for children in December.
