FACEBOOK has been accused by members of Lee Rigby's family of having "blood on its hands" after it emerged that one of the fusilier's killers had used the social media network to reveal his intention to kill a soldier.

It is an understandable reaction from a family in mourning after a loved one was taken from them in horrific circumstances.

But it is not a view we share. Indeed, we agree with former MI6 director Richard Barratt that it is an unfair accusation.

Social media operators should, of course, be responsible enough to sound the alarm when messages are posted which raise significant suspicions of criminal activity.

But how realistic is it to expect Facebook to monitor every posting? The company has 25 million users, generating something like 125 million posts a day. It would be like looking for a needle in acres of haystacks.

We believe there is a responsibility to act if suspicious postings are drawn to a media company's attention. That applies to The Northern Echo's own website, just as much as it does to Facebook.

There is a growing case for that responsibility to be formalised in legal guidelines.

But we must also recognise that policing the web with 100 per cent efficiency is an impossible task.

And that's why the millions of law-abiding, responsible people who are out there on social networks have a valuable role to play in helping the police and intelligence services to nip terror plots in the bud.