Access to social media will be banned in the UK for users under 16, Keir Starmer has announced, in what he described as “real change for our children and our future”.

“Social media is making children unhappy, it’s making it easier for bullies to harass and abuse them, and it could even be harming their mental health,” he said, setting out plans briefed over the weekend, which will go further than a pioneering ban in Australia.

The plan includes a ban on all the main social platforms with separate restrictions on online products such as gaming apps, including removing the option to chat to strangers.

“This is not something I do lightly, and I will not present it as cost-free, as if social media has [brought no] benefits to young people, because clearly that is wrong,” he said. “But government is always about choices, and it’s clear to me that a total ban is the right choice.”

Detailed in a speech at Downing Street, the changes were implicitly set out as a legacy of Starmer’s time as prime minister, given he is expected to face a leadership challenge soon. He said the ban was part of a way to reassure parents that “Britain will be better for their children, that they will get a fair chance”.

He said predictions that many teenagers would circumvent the ban, as in Australia, was not the point.

“We don’t say, ‘Oh, look, a teenager managed to get a drink somehow, so let’s not bother banning alcohol sales for children.’ We don’t do that, do we?

“I just don’t accept that. Our laws are rules, but they’re also an expression of our values. They shape the social contract, and so 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, full freedom to grow up, more opportunity, and that, at the end of the day, is what this government is about.”

Answering questions after the speech, Starmer said the aim would be to pass legislation by the end of the year, with the ban coming into force by next spring.

Starmer made the announcement in front of an audience that included a number of campaigners for a ban, including parents who had lost children, whom he thanked.

He said: “I am not prepared to compromise on the safety and happiness of our children, and that is why this ban must happen, and that is why this ban will happen.

“Yes, it’s hard – hard to legislate for, hard to regulate, hard to enforce. That’s why we sought a wide range of views on this. That’s why we listened to people, had a conversation, we looked carefully at the evidence, learned from countries like Australia that are taking similar steps.”

Asked if he expected a backlash from US tech giants, Starmer argued the ban did not mean he was opposed to technology and AI.

“I do not accept, and I will never accept that you can’t be both pro tech and AI, and at the same time say we must protect our children.

“I’m never going to accept the argument that for the future of AI and tech, we must leave our children exposed in the way that they have been, or they might be in the future.”

The government said on Sunday that nine in 10 parents backed a minimum age of 16 for accessing the apps in responses supplied to its “growing up in the online world” consultation.