Three of the world’s largest telecommunication companies, Verizon, Vodafone and BT, are providing the U.K.'s intelligence agency with their customers’ phone, email and Facebook data, the Guardian reported.

According to the British paper, top secret documents provided by former U.S. National Security Agency (NSA) contractor Edward Snowden and originally published in the German paper Süddeutsche, have implicated the three major telecom firms—along with four other companies—in granting the U.K. Government Communications Headquarters (GCHQ) unlimited access to their undersea cables.

As revealed by Snowden earlier this week, the NSA has paid the GCHQ over $150 million in the past three years for access to British intelligence, meaning that 250 NSA agents can view the GCHQ’s data.

Last year, the GCHQ apparently tapped more than 200 fibreoptic cables carrying both Internet and phone data. The agency stores metadata--information about when and where messages are sent--for up to 30 days. The content of communications are only stored for three days.

The data is searched by the NSA using the “XKeyscore” program, which the NSA has called its “widest-reaching” operation. The program allows agents to query massive databases of emails, browsing histories, and chats (in real time) without a warrant. 

An earlier batch of documents disclosed by Snowden revealed that the NSA also gave German intelligence access to the XKeyscore program. Whether the Germans had access to the GCHQ’s data is unclear.

According to one of the Guardian’s confidential sources who is “familiar” with GCHQ intelligence, “if you had the impression we are reading millions of emails, we are not...The vast majority of the data is discarded without being looked at...we simply don't have the resources."

Verizon stands out as the only American telecom firm aiding the British spy agency. The U.S. company’s partnership with foreign intelligence can perhaps partially be explained by its close relationship to U.K.-based Vodafone, which owns 45 perecent of its wireless business. 

The Guardian had already reported that GCHQ was tapping telecom companies’s cables, but until now the names of those firms remained secret. One document provided to the paper by Snowden warned that disclosing the names could lead to “high-level political fallout.” That risk seems highest for Verizon, the largest company on the list for whom the GCHQ is a foreign agency.

The other four companies that have given the GCHQ access to their submarine cables are Global Crossing, Level 3, Viatel, and Interoute. Together they give the British intelligence agency access to a large share of the world’s Internet communications.  

“They are worse than the U.S.," Snowden told the Guardian.

Photo by Cory Doctorow/Flickr