He did not name Russia directly, but he said that “hostile” states were trying to “further their aims” via “cyber-attacks, propaganda [and] subversion of democratic process”.

“Our job is to … shine a light on these activities and to help our country and our allies, in particular across Europe, build the resilience they need to protect themselves,” he said.

“The risks at stake are profound and represent a fundamental threat to our sovereignty; they should be a concern to all those who share democratic values”, he added.

The term hybrid warfare is commonly used to refer to Russia’s mix of covert military action, economic, and information warfare, as showcased in its attack on Ukraine.

US intelligence chiefs in October publicly accused Russia of disrupting the American elections.

They said “Russia’s senior-most officials” had authorised the hacking and leaking of emails from the Democratic Party to help its rival, the Russia-friendly Donald Trump, who went on to win.

Adam Schiff, a Democratic senator on the intelligence committee, also said at the time: “We’re … encouraging the [US] administration to work with our European partners, who have been the subject of even worse meddling, to coordinate a response to this”.

The concerns have been echoed by German spy chiefs and by chancellor Angela Merkel, who will fight for re-election next year against the Russia-friendly SPD party and the anti-EU AfD party.

Hans-Georg Maassen, the head of Germany’s BfV domestic intelligence agency, said in a statement on Thursday that Russia’s "disinformation" campaign aimed to “weaken or destabilise the Federal Republic of Germany.”

He added: “We see aggressive and increased cyber spying and cyber operations that could potentially endanger German government officials, members of parliament and employees of democratic parties”.

Bruno Kahl, the head of Germany’s foreign service, the BND, told Sueddeutsche Zeitung, a German newspaper, in November, that “cyber-attacks are taking place that have no purpose other than to elicit political uncertainty”.

“The perpetrators are interested in delegitimising the democratic process as such … We have indications that [the attacks] come from the Russian region”.

France and Italy

France will also hold elections next year, with the Kremlin-funded and anti-EU National Front party doing well in polls.

Italy just held a referendum that toppled its pro-EU leader, Matteo Renzi, and boosted the standing of the anti-EU and Russia-friendly 5 Star Movement Party.

La Stampa, an Italian newspaper, reported that Russia-based blogs and social media accounts has promulgated fake news designed to harm Renzi.

Laura Boldrini, the parliament speaker, said afterward that Italy had to “act now” to halt media attacks.

Massimo D’Alema, a former Communist Italian PM, mocked the Russia allegations, however.

“I don’t believe there is dark, organised centre, a group of hackers in the Kremlin trying to affect the Italian referendum … I think they could care less”, he said.

Augustus Henning, a former head of Germany’s BND spy service, has also doubted the extent of Russia’s influence in Europe.

“I don’t see that Czechia is really challenged by Russia, nor is Poland’s internal structure. I don’t think Russia is so strong in the West”, he recently told EUobserver.

“The problem for Russia is that they don’t offer a very attractive model of society or the economy”, he said.

Brexit and Trump

With the UK preparing to leave the EU, Younger, the MI6 chief, said on Thursday that Britain would uphold intelligence cooperation “with our European partners, France and Germany foremost amongst them”.

With Trump’s win in the US creating further uncertainty on Western unity, Younger added: “I’m often asked what effect the big political changes of 2016, Brexit and the US election result, will have on these relationships. My answer is that I will aim for, and expect, continuity”.

“These relationships are long lasting and the personal bonds between us are strong. The threats that we faced before these events have not gone away”, he said.