In our manifesto, the Government set out our commitment to redoubling efforts to counter extremism, including online, to stop people being radicalised and drawn towards hateful ideologies. A number of strands of activity have been established to progress this work, which, among other things, have led to the appointment of an interim Prevent commissioner, Lord Anderson, to drive improvements. We have published plans to introduce youth diversion orders to tackle young people at risk of terrorism.
Many documents produced across Government as part of commissioned work are not implemented and do not constitute Government policy. This work did not recommend an expansion in the definition of extremism, and there are not and have never been any plans to do so. To be clear, the leaked documents were not current or new Government policy.
As we have said repeatedly, Islamist extremism followed by far-right extremism are the biggest threats we face. Last week, the Home Secretary set out our plans to carry out an end-to-end review of Prevent thresholds on Islamist extremism, because we are concerned that the number of referrals is too low. Ideology, particularly Islamist extremism followed by far-right extremism, continues to be at the heart of our approach to countering extremism and terrorism.
But, as the horrific Southport attack shows, we also need more action on those drawn towards mixed ideologies and violence-obsessed young people. As the Home Secretary set out in the House last week, there has been a troubling rise in the number of cases involving teenagers drawn into extremism, including Islamist extremism, far-right extremism, mixed and confused ideologies, and obsession with violence. This includes a threefold increase in under-18s investigated for involvement in terrorism. Some 162 people were referred to Prevent last year for concerns relating to school massacres. Our Five Eyes counter-terror partners have also warned about the growing radicalisation of teenagers and young people.
We will continue to drive work to counter the most significant extremist threats in the weeks and months ahead, as the Home Secretary and the Prime Minister have already set out.