Edward Snowden, the whistleblower who revealed secret government spying programmes, has been charged with espionage by US authorities. A provisional arrest warrant has been issued and Hong Kong authorities have been asked to detain him. US prosecutors have filed a criminal complaint, charging Mr Snowden with three offences including unauthorised communication of national defence information, which comes under the Espionage Act, and theft of government property. He is also charged with willful communication of classified communications intelligence information to an unauthorised person. All three crimes listed carry a maximum 10-year prison penalty. The former CIA technician, who has worked for America’s National Security Agency (NSA), leaked details of American telephone and internet surveillance programmes. He revealed the existence of a surveillance system called Prism that was set up by the NSA to track the use of the internet directly from ISP servers. The NSA and FBI have said that the secret programme provided “critical leads” in preventing “dozens of terrorist events” – although some terror experts dispute the claims. President Obama has also said the programmes were carried out with “systems of checks and balances” and overseen by the courts and the US Congress. The Prism revelations sparked outcry in the UK when The Guardian reported that the GCHQ eavesdropping agency had been accessing information about British citizens through Prism. Mr Snowden fled to Hong Kong on May 20 after copying the last set of documents he intended to disclose at the NSA’s office in Hawaii.