Theresa May is to introduce new laws to combat Islamist extremism following the murder of US journalist James Foley, allegedly by a British jihadist.
The Home Secretary said Britain must introduce all the legal powers necessary to fight "deadly extremist ideology" which could take "decades" to eradicate, in an article for the Daily Telegraph.
Mrs May's plans include: an "anti-social behaviour order" for extremists, making it illegal to join extremist groups that are not directly involved in terrorism, and stripping dual nationals of their citizenship.
Britain was "in the middle of a generational struggle" against extremism, she added.
May's intervention comes amid growing calls to toughen terror laws in the wake of James Foley's death.
A British family have told ITV News of their devastation after discovering a close relative is fighting with the Islamic State in Iraq.
A French journalist who was held hostage with James Foley in Syria has told ITV News it was "devastating" to see his murder.