Children aged eight to 17 spend between two and five hours online per day, according to Ofcom research.
Children have to be at least 13 to create their own social media profile, with stricter rules on age checks having come into force in July.
The new regulations also introduced new rules requiring platforms to change the algorithms which determine what is shown in children's feeds.
The Liberal Democrats have previously pushed unsuccessfully to raise the age at which tech companies can collect children's data from 13 to 16.
The Labour government is currently considering a two-hour cap on the use of individual social media apps for children, along with a 22:00 curfew.
But in her speech, Collins said that ministers "make noise" about online safety but had yet failed to deliver on promises of stronger time curbs.
Ministers have also previously faced pressure from the Conservatives to legislate for an England-wide ban on smartphones in schools.
Labour has so far stopped short of legislating for such a ban, although it has said it is reviewing guidance that allows individual headteachers to ban the devices.