A CHINESE tracking device was found hidden in a UK government car, according to an intelligence officer.
Officials forensically searched vehicles amid growing security fears and found "disturbing things" during the sweep.
A serving security source said at least one SIM card able to transmit location data was discovered inside the sealed part of a car imported from China.
The vehicles searched are often used by diplomats and senior members of the government.
A serving security intelligence officer said the vehicles were "surgically dismantled to the last nut and bolt" amid concerns Chinese intelligence services have been targeting UK ministers.
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The source told inews: "It [the SIMs] gives the ability to survey government over a period of months and years, constantly filing movement, constantly building up a rich picture of activity.
"You can do it slowly and methodically over a very, very long time. That's the vulnerability."
According to a former GCHQ analyst, the aim is "more about quantity" and to fit as many as possible to "pinpoint in on sights of interest".
It is understood Chinese car parts are fitted without being opened because of warranty and commercial agreements.
Former Tory leader Sir Iain Duncan Smith has called for China to be recognised as a threat to the UK.
He told the outlet: "I don’t know how much more the UK needs to know about the threat China poses to us all.
"Surely it is time to change the integrated review and refer to China as a systemic threat."
It comes after MPs also said China should be officially deemed a "threat" to the UK, with the countries' economic ties diluted to allow Britain to stand up for its values.
But a potentially risky shift towards stronger language should be avoided unless the Government can commit to meaningful action, the Commons Foreign Affairs Committee (FAC) last month warned.
In a report on updating the Integrated Review (IR) of defence and foreign policy, the FAC called for the UK to bolster its resilience to international threats - including China - if it is to remain a global "heavyweight".
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To achieve this, the committee recommended bringing in a new "national resilience lead" and launching regular cross-government meetings on the issue.
Chairwoman Alicia Kearns said Britain's ability to respond to "seismic" global shocks has been "repeatedly tested" in recent years, from the Covid-19 pandemic to Russia's invasion of Ukraine.
These events have "exposed our vulnerability", making it "clear" the nation needs to become more resilient, she said, in particular by treading a "fine line" on relations with China.
The committee found Britain's dependency on the global power "constrains" its ability to defend its own interests and values, limiting its options when China "challenges the international order".
It warned China poses a "significant threat" to the UK on "many different levels", citing potential hazards such as intellectual property theft and the intimidation of British citizens.
Despite their concerns, the MPs said the Government should continue to work with China on "key areas", insisting this is vital for pursuing some global goals, such as the fight against climate change.