Work and Pensions Secretary Liz Kendall has said Nato countries are involved in a “hidden cyber war” with Russia.

Chancellor of the Duchy of Lancaster Pat McFadden will warn in a major speech next week that Russia is prepared to launch a series of cyber attacks on Britain and other Nato members as it seeks to weaken support for Ukraine.

Mr McFadden will say Moscow will “not think twice” about exploiting defence gaps to target UK businesses and allies must “not underestimate” the threat it poses.

Speaking to Sky News’ Sunday Morning with Trevor Phillips programme, Ms Kendall said her colleague was right to say “there is not only the open military war with Russia as the aggressor, but there is also a hidden cyber war and that Russia will do everything in its power to destabilise not only within Ukraine but amongst the Nato allies”.

She added: “So, we have to be absolutely vigilant in that as a Government, but also in businesses and wider society to protect against those cyber hacktivists.

“We have for many months … really focused on making sure we have all the protections we need including cyber protections because there is a threat from Russia, this hidden warfare, as well as the open military aggression.”

In a speech to the Nato cyber defence conference at Lancaster House, Mr McFadden is expected to warn that cyber interference enables Russia to “turn the lights off for millions of people” and represents the “hidden war” it is waging against Kyiv, as first reported by the Sunday Telegraph.

He will say: “Military hard-power is one thing. But cyber war can be destabilising and debilitating. With a cyber attack, Russia can turn the lights off for millions of people. It can shut down the power grids. This is the hidden war Russia is waging with Ukraine.

“Given the scale of that hostility, my message to members today is clear: no-one should underestimate the Russian cyber threat to Nato. The threat is real. Russia is exceptionally aggressive and reckless in the cyber realm.”

Pat McFadden stands outside the BBC HQ
Pat McFadden is to address the Nato cyber defence conference (Lucy North/PA)

Mr McFadden is expected to specifically call out Unit 29155, a Russian military unit the Government says was previously found to have carried out a number of attacks in the UK and Europe.

There are gangs of “unofficial hacktivists” and mercenaries not directly under the Kremlin’s control “but who are allowed to act with impunity so long as they’re not working against Putin’s interests”, he will say.

It comes after South Korea, a Nato Indo-Pacific partner, was targeted in response to its monitoring of the deployment of North Korean troops to Kursk, where Russia is fighting against Ukraine.

The attack has been widely attributed to a pro-Kremlin cyber gang, with Mr McFadden warning that such groups act with “disregard” for geopolitics and “with just one miscalculation could wreak havoc on our networks”.

The Cabinet Office minister is expected to set out details of how the UK will seek to boost its protections against emerging cyber threats in a speech on Monday, as well as how the country is stepping up work with Nato allies.

He and senior national security officials will also meet business leaders next week to discuss how they can protect themselves.