Internet firms need to act to prevent terrorists from plotting "murder and mayhem" on their networks, the Prime Minister has argued.
David Cameron made the comments after the release of a report by the government's Intelligence and Security Committee, which raised concerns over some social media companys' policies when it came to tackling suspicious behaviour online.
ITV News UK editor Rohit Kachroo reports:
Lee Rigby's stepdad and sister criticised social media companies for failing to notify the authorities of users plotting a terror attack.
ITV's UK Editor Rohit Kachroo looks at the findings of a report into the extent of intelligence agencies' knowledge of Lee Rigby's killers