Moscow is planning to ramp up its nuclear threats on the UK and Europe in a bid to break Nato’s resolve, defence insiders and experts have warned.

Russian state TV issued a chilling warning to Britain this week that Moscow could deploy its nuclear-armed autonomous “super torpedo”, Poseidon, in retaliation for UK-made drones being used by Ukraine to strike Russia.

Vladimir Putin’s regime claims the missile can strike coastal cities underwater at 120mph and cause radioactive tsunamis that would wreak widespread devastation.

But Western military experts say the alarmist rhetoric is nothing more than verbal threats and Russia is not planning to carry them out because it would trigger an all-out nuclear war with Nato.

Instead, in the short term, Moscow is expected to send a message to the UK in response to the use of British-made drones by escalating its grey zone warfare or more overt activity – below the threshold of triggering Nato’s Article 5. Such tactics could include expelling diplomats, firing warning shots near a UK-owned oil rig or even seizing a UK plane or ship.

However, the ramped-up threats over Russia’s nuclear arsenal appear to be part of a strategy designed to unnerve Britain and its European allies and attempt to destabilise Nato at a time when Donald Trump is already going cool on the alliance.

This so-called “nuclear signalling” is becoming an increasingly used propaganda tool alongside its hybrid warfare of cyber attacks and “shadow fleet” patrols of Nato waters.

Putin is facing significant challenges in the Ukraine war having suffered heavy military losses, and the conflict placing strain on the economy. Recent Ukrainian attacks on oil infrastructure and Wildberries, Russia’s version of Amazon, have also had an impact.

Professor Katarzyna Zysk, professor of international relations and contemporary history at the Norwegian Institute for Defence Studies, said: “Russia does not need every nuclear signal to be believed, but it needs the possibility of escalation to remain sufficiently credible to try to influence Nato. That residual uncertainty can still constrain Nato decision-making.”

This week Russia claimed it had tested its newest sub, the , which it says can carry Poseidon missiles, in the White Sea, and Putin has previously boasted that his military has carried out successful testing of the super torpedo weapon.

Although there are major question marks over whether Poseidon really has the capabilities that Moscow claims, unlike the country’s aerial missiles, which can be intercepted in flight, Nato has nothing in its arsenal to stop such a weapon.

Moscow ‘trying to isolate Britain’

General Sir Richard Barrons, former British Joint Forces commander and co-author of the UK Strategic Defence Review, said Moscow wanted to try to isolate Britain by talking up its nuclear threats to our coastline.

He told The i Paper that the changing nature of the relationship between the Trump administration and Moscow meant the US was no longer “in the face of President Putin on behalf of the West”.

Barrons added: “They have a different relationship, and the UK is regularly singled out as number one enemy for Russia. There’s really nothing new in the fact that weapons the UK has provided or made are being fired into Russia. That’s been happening for a long time now.

“What makes it new is this developing sense of the US cavalry not coming, so that makes it easy to talk up threats against big European players because you’re pretty confident that the US is going to keep out of it now.”

Barrons said Russia is expected to “dial up” its activities just below the level of open warfare to irritate Europe “in the context where everyone can feel what’s happening in Ukraine coming to some sort of culmination”.

A provoked Europe would be more powerful than Russia

He added: “Russia likes to let the UK and the rest of Europe know that if it wanted to, it’s got the tools to really hurt, and it has the habit of saying those things in order to deter us from doing the things we’re doing, like supporting Ukraine.

“But Europe is way more powerful than Russia … Russia would be beyond crazy to attack Europe because a Europe stirred will be massively more powerful. And of course, the UK uniquely has an independent strategic nuclear deterrent, and so, it has an assurance that only France has in Europe.”

Barrons said he did not think any western armed forces or intelligence had seen Poseidon, but added: “Russia have talked it up, and it has become clear that they [Moscow] at least believe they have it.

“And it is a worrying thing because if you live on an island with lots of littoral [coastline], there is no way of stopping it. Anti-ballistic missiles don’t work with Poseidon, and so you would have a nuclear weapon slamming into a coastal city, such as New York.

“I think there’s very little doubt it exists”.

He said that, like other strategic nuclear weapons, Poseidon’s primary value lies in deterrence and political messaging, since any use of it would almost certainly trigger a retaliatory nuclear response.

“It is basically in the traditional basket of Russian threatening behaviour.”

Threats give Putin more room for manoeuvre

Zysk said Russia’s use of the threat of nuclear weapons to influence or constrain the behaviour of other countries, rather than actually using those weapons, would “widen the space in which the Kremlin believes it can operate below the threshold of direct Nato-Russia conflict”.

Her theory is that Russia’s nuclear signalling can make Nato countries more risk-averse, creating more space for the Kremlin to carry out cyber hacks, sabotage, espionage and other grey-zone activities.

“Russia’s nuclear arsenal provides a strategic backdrop against which Moscow conducts more aggressive non-military/hybrid operations, while at the same time trying to limit the risk of direct confrontation with Nato,” she said.

“Reminding Nato about systems such as Poseidon and [a Russian nuclear cruise missile] aim to reinforce Russia’s broader coercive strategy [of using pressure and intimidation to influence other countries’ decisions], even when they do not constitute credible threats at this moment.”

Zysk said while Russia overused its nuclear threats during the first year of its war with Ukraine, reducing its credibility, “a diminished credibility is not the same as irrelevance”.

“Even though the public discourse on possible nuclear use has been less prominent, Russia has continued its aggressive nuclear-signalling campaign, nonetheless,” she added.

“The Russian TV presenters referring to Poseidon and in the report on UK-made drones fits this pattern. While Russian state TV does not always take direct speaking notes from the Kremlin, it is still an important element of the information environment that can help to magnify signals directed at the public at home and abroad.”