The pessimism reflects concern that Russia may be winning a so-called hybrid war with Europe, weakening the options available to Nato war planners in the event of military conflict.

The surge in support for the populist forces in Europe’s main military states is also endangering proposals for a group of five European countries, including the UK, to take on a new coordination role as the US prepares to reduce its commitments to the conventional defence of Europe.

Defence officials, speaking at a forum convened by the Munich Security Conference (MSC), the leading security foundation, said the European public may not have the appetite for a prolonged war, requiring Nato to focus its plans on a relatively quick conflict.

One recent British cabinet member admitted the west had been “crap” at educating its public about the scale of the hybrid conflict with Russia. Another UK diplomat claimed successive British prime ministers had done nothing to explain the scale of the threat.

They said this had left ministers locked in an unenviable task of persuading unprepared voters to cut welfare spending to fund defence. “The level of the debate has been at that of a kindergarten,” the UK diplomat admitted.