Conspiracy theories have become a mainstream cultural phenomenon. This paper considers the role they play in extremist groups and counterterrorism work. It presents the first ever analysis of conspiracy theories in the ideology and propaganda of fifty extremist groups: religious, far-right and left, eco, anarchic and cult-based.

It is argued that conspiracy theories are a ‘radicalising multiplier’, which feed back into the ideologies, internal dynamics and psychological processes of extremist groups in three ways. Firstly, they create demonologies of ‘the enemy’ that the group defines itself against. Secondly, they delegitimise voices of dissent and moderation. And thirdly, they encourage a group or individuals to turn to violence, because it acts as rhetorical devices to portray violence as necessary to ‘awaken’ the people from their acquiescent slumber. More broadly, conspiracy theories drive a wedge of distrust between governments and particular communities which can hinder community-level efforts to fight violent extremism.

It is, however, difficult for government to tackle conspiracies. The paper calls for government institutions to be more open, investment to enable young people to think critically and recognise propaganda, and for civil society to play a proactive role.