Russia is targeting the home internet networks of tens of thousands of households in Britain to spy on them and mount mass cyber-attacks, GCHQ and the FBI have warned.

The security services in both the US and the UK said that they are "confident" that Russia is hacking into "residential routers" which people use to connect to the internet, providing them with a "tremendous weapon" against the West.

In an extraordinary joint statement, GCHQ and the FBI also revealed that Russia is preparing to mount cyber attacks on Britain's "critical infrastructure" including energy networks, the emergency services and the armed forces.

Authorities in the US and the UK revealed that Russia has been probing the...