Britain could carry out offensive cyber attacks to tackle high-tech Russian subversion, the Defence Secretary has suggested.

Sir Michael Fallon said the UK and its Nato allies must now compete on the cyber battlefield as much as they do in conventional air, land and sea warfare.

Britain’s adversaries must know they face a price for using cyber weapons, Sir Michael warned in a speech describing how to cope with an increasingly aggressive Russia.

He said Britain was doubling its investment on defensive and offensive cyber warfare to £1.9bn.