It claimed that the primary targets were Ukrainian financial, energy and government sectors, but the indiscriminate design of the malware caused it to spread further, affecting other European and Russian businesses.
Update: Overnight, the White House also laid the blame for NotPetya on Russia. "In June 2017, the Russian military launched the most destructive and costly cyber-attack in history," a statement said.
Original story continues: Among some more prominent victims of the ransomware, which came to be known variously as Petya (nomenclature given to ransomware that already existed at the time), NotPetya, ExPetr, Nyetya and GoldenEye, were the US pharmaceutical company Merck, Russia's state oil company Rosneft, the shipping conglomerate Maersk and the UK-based advertising and public relations firm WPP.
Also badly hit were the banking, electric and gas sectors in Ukraine, with the malware spreading to the UK, Denmark and Spain.
The notice that appeared on Windows computers that were hit by the NotPetya ransomware in June last year.
The Russian security firm Global-IB said at the time that in Ukraine, large banks and enterprises, namely, Oschadbank, Ukrgasbank, Pivdenny Bank, OTP Bank, TASKombank, The Epicenter chain store, Kovalska industrial and construction group, three major Ukrainian telecom operators, Kyivstar, LifeCell, Ukrtelecom, were among those affected.
Lord Ahmad said: "The UK Government judges that the Russian Government, specifically the Russian military, was responsible for the destructive NotPetya cyber-attack of June 2017.
"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.
"The UK is identifying, pursuing and responding to malicious cyber activity regardless of where it originates, imposing costs on those who would seek to do us harm. We are committed to strengthening coordinated international efforts to uphold a free, open, peaceful and secure cyber space."
In a statement, Russia said it "strongly rejected" the "groundless accusations" by the UK that it was behind the NotPetya attack.
"We strongly reject such accusations, we consider them to be groundless, they are part of the similarly groundless campaign based on hatred against Russia," Russian presidential spokesman Dmitry Peskov said.
Ransomware affects Microsoft Windows systems in the main. Mac ransomware is very rare.
Graphic: courtesy Kaspersky Lab