China's spies are so sophisticated they can intercept any mobile phone call made across the UK, it is feared.
Agents can tap in by intercepting satellite and cable communications without being based here.
Alarm over China’s rising capability was first raised by Britain’s former top soldier General Lord Dannatt.
He warned Beijing’s spooks are able to listen to any non-encrypted call made between UK military and government officials.
The same fears can be said of industry figures, administrators and the public, if targeted by spies.
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A former military intelligence officer said: “China has a very sophisticated capability when it comes to phone intercepts.
“Military can assume their calls, if they aren’t encrypted, can be intercepted and no matter how innocent the calls may seem, they could be of value.
“Meeting timings, names of other callers, dates, times and places, everything when fed into the general intelligence picture can be cross referenced to gain valuable information.
"And that means you can assume the same can be said of any member of the public.”
Lord Dannatt, who rose to Chief of the General Staff in 2006, warned recently China’s spooks had been eavesdropping in the UK for at least five to 10 years.
He said: “I believe that any private conversation between anybody who’s got a foreign and defence background should assume the Chinese are listening.
“Chinese eavesdropping has been going on for quite some time.
“We talk about industrial secrets but not many are secret.
"I have it on good authority that where the Chinese choose to listen they can.
"So what we have regarded as secret and confidential we shouldn’t actually make those assumptions in the future.”
The general spoke out after the Government said last week it wanted to have a positive relationship with China despite the nation being a security threat.
