Russian intelligence agencies are covertly funding and working with European environmental groups to campaign against fracking and maintain EU dependence on Russian gas, the head of Nato has claimed.

Answering questions after a speech in London, Anders Fogh Rasmussen, Nato secretary-general, said improving European energy security was of the “utmost importance” and accused Moscow of “blackmail” in its dealings with Europe.

“I have met allies who can report that Russia, as part of their sophisticated information and disinformation operations, engaged actively with so-called non-governmental organisations – environmental organisations working against shale gas – to maintain European dependence on imported Russian gas,” Mr Rasmussen, former Danish prime minister, told an audience at Chatham House, the international affairs think-tank.