MI5 is also trying to send a signal to China with spying warning to parliamentarians

The warning was meant for British parliamentarians, of course, but MI5 and the government are also trying to send a signal to China.

We know what you are doing, and in ministers' words today we "won't stand for it".

But in the wake of the collapsed China spying case last month, the security services also want to reestablish a badly dented sense of deterrence.

Politics latest: China responds to MI5's spy warning to MPs

That case against two British men accused of spying for Beijing fell apart because officials would not use the words "enemy" or "national security threat" to describe China.

The failure projected a sense of weakness in the face of Chinese espionage efforts, something the government is keen to dispel.

Those efforts remain persistent and dangerous, security officials insist.

China has always aggressively sought the official and commercial secrets of Western nations.

It regards that mission as a patriotic duty, an essential part of a national project to catch up with and then overtake the West.

In the words of Britain's security minister, Dan Jarvis, on Tuesday, China seeks "to interfere in our sovereign affairs in favour of its own interests".

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Parliamentarians warned of spying attempts from China agents

Indeed, much of China's technological and economic progress was, until recently, built on intellectual property stolen from rival nations.

Its private sector has been notorious for ripping off and reverse engineering Western know-how, pilfered from joint venture partners or through commercial espionage.

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Intelligence agencies say the Chinese have also hoovered up vast amounts of personal data from all of us through social media platforms like TikTok and other methods, collecting in bulk for now, for sifting and harvesting later.

Officially, the Chinese government denies all these allegations. It has to be said that Western spies are also hard at work snooping on China.

But critics say Western nations have been naive and too trusting of the Chinese threat.

While the British government remains unsure whether to identify China as an enemy or simply a commercial rival, an ambivalence remains, which Beijing will continue doing its best to exploit.