The culture secretary has agreed he does not have enough power to police social media firms after admitting only four of 14 invited to talks showed up.
Matt Hancock told the BBC it had given him “a big impetus” to introduce new laws to tackle what he has called the internet’s “Wild West” culture.
He admitted self-policing had not worked and legislation was needed.
But he did not answer questions about what it would take for companies to be hit with huge fines.
He told BBC One’s Andrew Marr show, presented by Emma Barnett, that the government “just don’t know” how many children of the millions using using social media were not old enough for an account and he was “very worried” about age verification.
Asked what the threshold would be for firms to be hit with fines, in terms of underage children on certain platforms, he said: “I’m not going to give a figure because we are going to consult on it.”
He told the programme he “hopes we get to a position” where all users of social media users has to have their age verified.
Code of conducts would be examined he said as existing “terms of reference” were often not enforced properly. Asked how many of the 14 firms invited to attend government talks had showed up, he replied: “Four.”
He said: “One of the problems we have got is that we engage with Facebook, Google and Twitter and they get all of the press, they get all of the complaints in the public debate but there’s now actually a far greater number of social media platforms like musical.ly.
“They didn’t show up and the companies, they have now got over a million on their site.”
He said that this, and the difficulties getting Facebook’s Mark Zuckerberg to answer MPs’ questions showed Britain did not have the power needed: “That’s one of the reasons we are legislating.
“The fact that only four companies turned up when I invited the 14 biggest in gave me a big impetus to drive this proposal to legislate through.”
Pushed for details of how quickly social media firms would have to remove terrorist content to avoid a fine, he said: “We should be very ambitious,” but said a set timescale could mean companies “work up to that timescale”, while he would prefer them to do so “as quickly as possible”.
Two government departments are working on a White Paper expected to be brought forward later this year.