Russia was behind a devastating cyber attack on Ukraine’s banks, government and power grid, the Foreign Office has said.

Cyber experts at the National Cyber Security Centre say the GRU Russian military intelligence agency was almost certainly responsible for the NotPetya attack in June 2017.

The Foreign Office last night said the attack had masqueraded as criminal ransomware, but had in fact been a deliberate attack on the Ukrainian state.

The UK Government judges that the Russian government, specifically the Russian military, was responsible for the destructive NotPetya cyber attack.Lord Ahmad of Wimbledon, Foreign Office minister

Lord Ahmad of Wimbledon, Foreign Office minister for cyber security, said the decision to publicly blame Russia for NotPetya underlined that Britain would not tolerate malicious cyber activity.

He said: “The UK Government judges that the Russian government, specifically the Russian military, was responsible for the destructive NotPetya cyber attack. The attack showed a continued disregard for Ukrainian sovereignty. Its reckless release disrupted organisations across Europe, costing hundreds of millions of pounds.

“The Kremlin has positioned Russia in direct opposition to the West, yet it doesn’t have to be that way. We call upon Russia to be the responsible member of the international community it claims to be rather then secretly trying to undermine it.”

Mr Williamson said last month that Russia was spying on British energy supplies with a view to disrupting them, possibly by cyber attack.

He told The Telegraph: “We have entered a new era of warfare, witnessing a destructive and deadly mix of conventional military might and malicious cyber attacks.

“Russia is ripping up the rule book by undermining democracy, wrecking livelihoods by targeting critical infrastructure, and weaponising information. We must be primed and ready to tackle these threats.”