Starmer has signalled his government is preparing to take action to curb functions that keep young people hooked on social media.
That could see an end to features such as infinite scrolling or "streaks" that reward daily use of an app.
Such features "shouldn't be permitted", Starmer said in an interview with the Sunday Mirror.
"This is the platforms trying to get children to stay on for longer, to get addicted. I can't see that there's a case for that, and therefore I can see we're going to have to act."
The government has faced calls for an Australian-style to ban on social media for under-16s and Starmer said he was "open minded" about a ban, but was clear that things would change.
"We'll go through the consultation, but I think I'll be absolutely clear things will not stay as they are.
"This is going to change. I don't think the next generation would forgive us if we didn't act now."
His comments come days after a landmark court case in the United States that saw a jury find Meta and Google liable for a woman's childhood social media addiction.
In a potentially precedent-setting decision, the jury in California recommended the 20-year-old plaintiff be awarded $US6 million ($A8.7 million) in damages.
Starmer said the decision could mark "a turning point" leading to "much stricter content restriction".
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