Firms will be expected to activate built-in features to stop children accessing sexually explicit images.
The bereaved families of the victims of Valdo Calocane speak at a press conference in London.
Women desperate to be parents are being lured by illegal sperm donor delivery services on social media.
The prime minister has pledged "decisive" measures in response to calls for an Australia-style ban.
Detectives say they were called to the scene in north London just after midnight on Monday.