US prosecutors have charged a North Korean man alleged to have been involved in creating the malicious software used to cripple the UK’s National Health Service.

The 2017 incident left NHS staff reverting to pen and paper after being locked out of computer systems.

Park Jin Hyok is said to be linked to the Lazarus Group.

The hacking collective is also blamed for the hack on Sony Pictures in 2014.

The US Department of Justice alleged the North Korean-backed cyber group had caused major damage.

“The scale and scope of the cyber-crimes alleged by the complaint is staggering and offensive to all who respect the rule of law and the cyber norms accepted by responsible nations,” said the Assistant Attorney General for National Security, John Demers.

“The complaint alleges that the North Korean government, through a state-sponsored group; robbed a central bank and citizens of other nations; retaliated against free speech in order to chill it half a world away; and created disruptive malware that indiscriminately affected victims in more than 150 other countries, causing hundreds of millions, if not billions, of dollars’ worth of damage.”

North Korea routinely denies being involved in hack attacks attributed to them.

Mr Park is charged with one count of conspiracy to commit computer fraud and abuse, and wire fraud.

Prosecutors said Mr Park was believed to be in North Korea.

“North Korea won’t be handing over this guy any time soon,” said Martyn Williams, a North Korea observer and journalist.

“So it likely won’t mean much on that level, but it is a symbolic step for the US government to take.

“It helps put meat on the bones of the numerous reports that said North Korea was responsible and is a relatively rare move for the US government.”