Russia is launching regular cyber attacks on the UK in a doomed attempt to weaken the government’s support for Ukraine, according to a cabinet minister.

In a major speech on Monday, chancellor of the Duchy of Lancaster Pat McFadden will say Moscow is waging “a hidden war” against Nato countries away from the traditional battlefield.

He will say cyber was is “a daily reality – one where our defences are constantly being tested”.

But he will insist Vladimir Putin “will not be successful” and that the UK will continue to stand with Kyiv against Russian aggression.

Speaking at a Nato cyber defence conference at Lancaster House, McFadden will say: “Military hard-power is one thing. But cyberwar 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.

“In the last year, both the Russian military and its unofficial army of cyber criminals and hacktivists have not just stepped up their attacks, but widened their targets to a number of Nato members and partners.

“The aim is to gain a strategic advantage and degrade the states that support Ukraine. In the UK, Russia has targeted our media, our telecoms, our political and democratic institutions, and our energy infrastructure.”

McFadden will add: “Be in no doubt: the United Kingdom and others in this room are watching Russia. We know exactly what they are doing, and we are countering their attacks both publicly and behind the scenes.

“We know from history that appeasing dictators engaged in aggression against their neighbours only encourages them. Britain learned long ago the importance of standing strong on the face of such actions.

“That’s why we support Ukraine in its fight to decide its own destiny. Putin is a man who wants destruction, not peace. He is trying to deter our support for Ukraine with his threats. He will not be successful.”

Describing Russia as “exceptionally aggressive and reckless in the cyber realm”, the minister will also say that businesses need to be on their guard.

“It is happy to exploit any gap in our cyber or physical defences,” McFadden will say. “It means making sure that businesses and other civilian organisations are doing everything they can to lock their own digital doors. Their security is our security.”