The US National Security Agency and the British government have secretly been unravelling encryption technology that billions of internet users rely upon to keep their electronic messages and confidential data safe, according to internal US government documents.

The NSA has bypassed or fully cracked much of the digital encryption used by businesses and everyday web users, according to reports in The New York Times, Guardian newspaper and on news website ProPublica.

The reports describe how the NSA invested billions of dollars over the last 13 years to make everyone’s secrets available for government consumption.

In doing so, the NSA built powerful supercomputers to break encryption codes and partnered with unnamed technology companies to insert “back doors” into their software, the reports claimed.

Such a practice would give the government access to users’ digital information before it was encrypted and sent over the internet.

A 2010 briefing about NSA work meant for its British counterpart GCHQ explained: “For the past decade, NSA has led an aggressive, multipronged effort to break widely used internet encryption technologies.”

The revelations stem from documents leaked by former NSA contractor Edward Snowden, who sought asylum in Russia this summer.

His leaks revealed a massive effort by the US government to collect and analyse all sorts of digital data that US citizens send at home and around the world.

Those revelations prompted a renewed debate in the US about the proper balance between civil liberties and keeping the country safe from terrorists.

President Barack Obama said he welcomed the debate and called it “healthy for our democracy” — but the Justice Department still charged Mr Snowden under the Espionage Act.

The reports described how some of the “most intensive efforts” focused on secure sockets layer, a type of encryption widely used on the web by online retailers and corporate networks to secure their internet traffic.

One document said GCHQ had been trying for years to exploit traffic from popular companies like Google, Yahoo, Microsoft and Facebook.