'These horrendous crimes were committed by sick and evil individuals, in the name of a sick and evil ideology. A grotesque and perverse worldview - which has nothing to do with the Islam that I know.'
Amid much commentary on the cause of the attacks and the effect on the Muslim community, Mr Khan added bluntly: 'Extremism isn't a theoretical risk. Most British Muslims have come across someone with extremist views at some point - and so have I. It's affected my personal life, my friendships, and my career.
'People I knew as a boy have gone on to hold extremist views, and even to act on them in terrible ways.
'When I was a lawyer, as well as representing people who were badly treated by the police or their employers, I sometimes had the unpleasant job of representing people with extremist views.
'It was horrible - but it went with the job. I've lost count of the number of times I've had to challenge the hideous views of seemingly intelligent and articulate people.
'People who look and sound like normal Londoners, until they say that 9/11 was a Mossad conspiracy. That the Jewish workers in the twin towers were tipped off and escaped.
'That Western foreign policy is the cause of all the world's problems. That there could be a land of milk and honey, if there was an Islamic kalifate. I could go on.'
Mr Khan said that British Muslims have a 'special role' to play in tackling extremism.
He added: 'To defeat the extremists we simply must do more to stop radicalisation in Britain. It doesn't just affect us in these awful moments of violence and terror.
'It is a cancer eating at the heart of our society - all the time. And if we're honest - not enough has been done to root it out.
'And in this week of all weeks that makes me angry. Angry because for too long we have buried our heads in the sand.'
He went on: 'I believe that British Muslims have a special role to play in tackling extremism. A special role not because we are more responsible than others - as some have wrongly claimed. But because we can be more effective at tackling extremism than anyone else. Our role must be to challenge extremist views wherever we encounter them.
'To challenge this perverse ideology, and to insist that British values and Muslim values are one and the same.
'To give the next generation of Muslim leaders the confidence to own the debate and defeat the extremists.'