Social media websites like Facebook have "a duty of care" to alert authorities when users reveal their intentions to take part in an act of terrorism, the stepfather of murdered soldier Lee Rigby has told Good Morning Britain.
Ian Rigby criticised Facebook for not sharing more information with authorities when it emerged one of his stepson's killers, Michael Adebowale, had spoken of his plans to murder a solider in an exchange on the social media site ahead of the attack.
Adebowale and Michael Adebolajo drove into the soldier before hacking him to death near Woolwich Barracks in May 2013.
Speaking after the release of a report into the security failings in the run-up to the attack, Mr Rigby said it was "a necessary evil" for social media websites to share information with authorities in extreme cases.
- Watch Good Morning Britain from 6am to see the full interview
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