Australia has blocked a £6 billion deal to lease its biggest electricity grid to Chinese and Hong Kong investors because of “national security", following Britain’s decision to delay Hinkley Point nuclear power station.

The Australian move comes as the US authorities laid espionage charges against China General Nuclear Power (CGN), the state company which would have a one third stake in the Hinkley Point project. Theresa May has delayed a final decision on whether to allow this construction to go ahead amid concerns that China’s involvement could threaten British national security.

The US justice department has accused Allen Ho, a CGN engineer based in America, of conspiring with the firm to steal secret technology from the American nuclear power industry. The alleged conspiracy lasted for almost 20 years, from 1997 until April this year.

In Australia, the government expressed concern about the security risk posed by a plan for two bidders – one from Hong Kong, the other from mainland China - to take a 50.4 per cent stake in Ausgrid, the main electricity network in New South Wales, the nation’s largest state. The network serves 1.6 million homes and businesses in Sydney and beyond.

Scott Morrison, the treasurer or finance minister, noted that the grid covers the “critical” supply of power and communications to businesses and government. "The national security concerns are not country specific and relate to the transaction structure and the nature of the assets," he said.