The killing of a man on the streets of London this afternoon has sparked calls for the Government to revive plans to extend internet and email monitoring powers to the security services.
Labour ex-home secretary Lord Reid said such measures were "essential" to combating terrorism, warning it could otherwise take "some huge tragedy" to show the decision was wrong.
Former independent reviewer of terror laws Lord Carlile said it should provoke a "pause for thought" on the decision to drop the planned Communcations Data Bill from the Queen's Speech.
Speaking on BBC2's Newsnight, Lord Carlile said:
We have to learn proportionate lessons from what has occurred.
We mustn't rush to judgment. But we must ensure that the police and the security services have for the future the tools they need which will enable them to prevent this kind of attack taking place.
I hope that this will give the Government pause for thought about their abandonment for example of the Communcations Data Bill and possibly pause for thought about converting control orders into what are now called Tpims, with a diluted set of powers.