"The middle classes could become a revolutionary class, taking the role envisaged for the proletariat by Marx," says the report.

This theory is based on the growing gap between the wealthy on one hand and an urban underclass threatening social order.

"The world's middle classes might unite, using access to knowledge, resources and skills to shape transnational processes in their own class interest."

Marxism may also be revived because of global inequalities.

The long term trend towards moral relativism and pragmatic values will encourage people to seek the 'sanctuary provided by more rigid belief systems, including religious orthodoxy and doctrinaire political ideologies, such as popularism and Marxism.'

The report also outlines other future threats, including neutron weapons that kill people but leave buildings intact, unmanned weapons platforms in space, and brain implants that could control behaviour and turn people into unwilling weapons.

Rear Admiral Chris Parry, head of the MOD's Development, Concepts and Doctrine Centre responsible for the report, describes the assessments as 'probability-based, rather than predictive.'