More than 60 Labour MPs have called on the prime minister to impose a ban on under-16s access to social media platforms.
In a open letter to Sir Keir Starmer on Sunday, the 61 MPs said "successive governments" had done "too little to protect young people from... unregulated, addictive social media platforms".
They urged him to follow the example of Australia, which brought in a ban in December. Several other countries are said to be considering similar laws.
Sir Keir has not ruled out introducing a ban, saying "all options are on the table". The House of Lords is likely to vote this week on a cross-party amendment that would implement an Australia-style ban in the UK.