Edward Snowden
Whistleblower Edward Snowden has been charged with espionage

Britain's eavesdropping agency GCHQ is "worse" than the US's National Security Agency (NSA) when it comes to snooping on worldwide communications, says whistleblower Edward Snowden, who has been charged with espionage by US authorities for leaking details of the top-secret Prism programme.

The latest set of documents revealed by the Guardian indicate that the British agency was involved in widespread surveillance of internet and telephone communications across the world.

The report suggests that GCHQ was able to tap both civilians' and targeted suspects' communication systems by tapping fibre-optic cables. The agency, which runs the programme under the codename Tempora, also has the capacity to store the data it collects for up to 30 days, for analysis.

"It's not just a US problem. The UK has a huge dog in this fight. They [GCHQ] are worse than the US," Snowden said.

Meanwhile, the US Justice Department has formally charged the former CIA employee with espionage and theft of government property.

The US is believed to be preparing an extradition request to Hong Kong, where Snowden fled ten days ahead of his disclosure.

Snowden faces charges of theft of government property, unauthorised communication of national defence information and wilful communication of classified communications intelligence information to an unauthorised person.

The charges, dated 14 June, were filed in the federal court in Virginia.

If found guilty, Snowden could face ten years in prison for each of the charges. A provisional arrest warrant has also been issued, asking the Hong Kong police to detain the whistleblower.

Filing the charges is the first step by the US in its efforts to get Snowden extradited and tried, a process that could entail a long legal battle.

"I've always thought this was a treasonous act. I hope Hong Kong's government will take him into custody and extradite him to the US," said Bill Nelson, a Democratic senator and member of the Senate Armed Services Committee.